research limitations and how to overcome them

How to Write Limitations of the Study (with examples)

This blog emphasizes the importance of recognizing and effectively writing about limitations in research. It discusses the types of limitations, their significance, and provides guidelines for writing about them, highlighting their role in advancing scholarly research.

Updated on August 24, 2023

a group of researchers writing their limitation of their study

No matter how well thought out, every research endeavor encounters challenges. There is simply no way to predict all possible variances throughout the process.

These uncharted boundaries and abrupt constraints are known as limitations in research . Identifying and acknowledging limitations is crucial for conducting rigorous studies. Limitations provide context and shed light on gaps in the prevailing inquiry and literature.

This article explores the importance of recognizing limitations and discusses how to write them effectively. By interpreting limitations in research and considering prevalent examples, we aim to reframe the perception from shameful mistakes to respectable revelations.

What are limitations in research?

In the clearest terms, research limitations are the practical or theoretical shortcomings of a study that are often outside of the researcher’s control . While these weaknesses limit the generalizability of a study’s conclusions, they also present a foundation for future research.

Sometimes limitations arise from tangible circumstances like time and funding constraints, or equipment and participant availability. Other times the rationale is more obscure and buried within the research design. Common types of limitations and their ramifications include:

Theoretical: limits the scope, depth, or applicability of a study.
Methodological: limits the quality, quantity, or diversity of the data.
Empirical: limits the representativeness, validity, or reliability of the data.
Analytical: limits the accuracy, completeness, or significance of the findings.
Ethical: limits the access, consent, or confidentiality of the data.

Regardless of how, when, or why they arise, limitations are a natural part of the research process and should never be ignored . Like all other aspects, they are vital in their own purpose.

Why is identifying limitations important?

Whether to seek acceptance or avoid struggle, humans often instinctively hide flaws and mistakes. Merging this thought process into research by attempting to hide limitations, however, is a bad idea. It has the potential to negate the validity of outcomes and damage the reputation of scholars.

By identifying and addressing limitations throughout a project, researchers strengthen their arguments and curtail the chance of peer censure based on overlooked mistakes. Pointing out these flaws shows an understanding of variable limits and a scrupulous research process.

Showing awareness of and taking responsibility for a project’s boundaries and challenges validates the integrity and transparency of a researcher. It further demonstrates the researchers understand the applicable literature and have thoroughly evaluated their chosen research methods.

Presenting limitations also benefits the readers by providing context for research findings. It guides them to interpret the project’s conclusions only within the scope of very specific conditions. By allowing for an appropriate generalization of the findings that is accurately confined by research boundaries and is not too broad, limitations boost a study’s credibility .

Limitations are true assets to the research process. They highlight opportunities for future research. When researchers identify the limitations of their particular approach to a study question, they enable precise transferability and improve chances for reproducibility.

Simply stating a project’s limitations is not adequate for spurring further research, though. To spark the interest of other researchers, these acknowledgements must come with thorough explanations regarding how the limitations affected the current study and how they can potentially be overcome with amended methods.

How to write limitations

Typically, the information about a study’s limitations is situated either at the beginning of the discussion section to provide context for readers or at the conclusion of the discussion section to acknowledge the need for further research. However, it varies depending upon the target journal or publication guidelines.

Don’t hide your limitations

It is also important to not bury a limitation in the body of the paper unless it has a unique connection to a topic in that section. If so, it needs to be reiterated with the other limitations or at the conclusion of the discussion section. Wherever it is included in the manuscript, ensure that the limitations section is prominently positioned and clearly introduced.

While maintaining transparency by disclosing limitations means taking a comprehensive approach, it is not necessary to discuss everything that could have potentially gone wrong during the research study. If there is no commitment to investigation in the introduction, it is unnecessary to consider the issue a limitation to the research. Wholly consider the term ‘limitations’ and ask, “Did it significantly change or limit the possible outcomes?” Then, qualify the occurrence as either a limitation to include in the current manuscript or as an idea to note for other projects.

Writing limitations

Once the limitations are concretely identified and it is decided where they will be included in the paper, researchers are ready for the writing task. Including only what is pertinent, keeping explanations detailed but concise, and employing the following guidelines is key for crafting valuable limitations:

1) Identify and describe the limitations : Clearly introduce the limitation by classifying its form and specifying its origin. For example:

An unintentional bias encountered during data collection
An intentional use of unplanned post-hoc data analysis

2) Explain the implications : Describe how the limitation potentially influences the study’s findings and how the validity and generalizability are subsequently impacted. Provide examples and evidence to support claims of the limitations’ effects without making excuses or exaggerating their impact. Overall, be transparent and objective in presenting the limitations, without undermining the significance of the research.

3) Provide alternative approaches for future studies : Offer specific suggestions for potential improvements or avenues for further investigation. Demonstrate a proactive approach by encouraging future research that addresses the identified gaps and, therefore, expands the knowledge base.

Whether presenting limitations as an individual section within the manuscript or as a subtopic in the discussion area, authors should use clear headings and straightforward language to facilitate readability. There is no need to complicate limitations with jargon, computations, or complex datasets.

Examples of common limitations

Limitations are generally grouped into two categories , methodology and research process .

Methodology limitations

Methodology may include limitations due to:

Sample size
Lack of available or reliable data
Lack of prior research studies on the topic
Measure used to collect the data
Self-reported data

The researcher is addressing how the large sample size requires a reassessment of the measures used to collect and analyze the data.

Research process limitations

Limitations during the research process may arise from:

Access to information
Longitudinal effects
Cultural and other biases
Language fluency
Time constraints

The author is pointing out that the model’s estimates are based on potentially biased observational studies.

Final thoughts

Successfully proving theories and touting great achievements are only two very narrow goals of scholarly research. The true passion and greatest efforts of researchers comes more in the form of confronting assumptions and exploring the obscure.

In many ways, recognizing and sharing the limitations of a research study both allows for and encourages this type of discovery that continuously pushes research forward. By using limitations to provide a transparent account of the project's boundaries and to contextualize the findings, researchers pave the way for even more robust and impactful research in the future.

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The limitations of the study are those characteristics of design or methodology that impacted or influenced the interpretation of the findings from your research. Study limitations are the constraints placed on the ability to generalize from the results, to further describe applications to practice, and/or related to the utility of findings that are the result of the ways in which you initially chose to design the study or the method used to establish internal and external validity or the result of unanticipated challenges that emerged during the study.

Price, James H. and Judy Murnan. “Research Limitations and the Necessity of Reporting Them.” American Journal of Health Education 35 (2004): 66-67; Theofanidis, Dimitrios and Antigoni Fountouki. "Limitations and Delimitations in the Research Process." Perioperative Nursing 7 (September-December 2018): 155-163. .

Importance of...

Always acknowledge a study's limitations. It is far better that you identify and acknowledge your study’s limitations than to have them pointed out by your professor and have your grade lowered because you appeared to have ignored them or didn't realize they existed.

Keep in mind that acknowledgment of a study's limitations is an opportunity to make suggestions for further research. If you do connect your study's limitations to suggestions for further research, be sure to explain the ways in which these unanswered questions may become more focused because of your study.

Acknowledgment of a study's limitations also provides you with opportunities to demonstrate that you have thought critically about the research problem, understood the relevant literature published about it, and correctly assessed the methods chosen for studying the problem. A key objective of the research process is not only discovering new knowledge but also to confront assumptions and explore what we don't know.

Claiming limitations is a subjective process because you must evaluate the impact of those limitations . Don't just list key weaknesses and the magnitude of a study's limitations. To do so diminishes the validity of your research because it leaves the reader wondering whether, or in what ways, limitation(s) in your study may have impacted the results and conclusions. Limitations require a critical, overall appraisal and interpretation of their impact. You should answer the question: do these problems with errors, methods, validity, etc. eventually matter and, if so, to what extent?

Price, James H. and Judy Murnan. “Research Limitations and the Necessity of Reporting Them.” American Journal of Health Education 35 (2004): 66-67; Structure: How to Structure the Research Limitations Section of Your Dissertation. Dissertations and Theses: An Online Textbook. Laerd.com.

Descriptions of Possible Limitations

All studies have limitations . However, it is important that you restrict your discussion to limitations related to the research problem under investigation. For example, if a meta-analysis of existing literature is not a stated purpose of your research, it should not be discussed as a limitation. Do not apologize for not addressing issues that you did not promise to investigate in the introduction of your paper.

Here are examples of limitations related to methodology and the research process you may need to describe and discuss how they possibly impacted your results. Note that descriptions of limitations should be stated in the past tense because they were discovered after you completed your research.

Possible Methodological Limitations

Sample size -- the number of the units of analysis you use in your study is dictated by the type of research problem you are investigating. Note that, if your sample size is too small, it will be difficult to find significant relationships from the data, as statistical tests normally require a larger sample size to ensure a representative distribution of the population and to be considered representative of groups of people to whom results will be generalized or transferred. Note that sample size is generally less relevant in qualitative research if explained in the context of the research problem.
Lack of available and/or reliable data -- a lack of data or of reliable data will likely require you to limit the scope of your analysis, the size of your sample, or it can be a significant obstacle in finding a trend and a meaningful relationship. You need to not only describe these limitations but provide cogent reasons why you believe data is missing or is unreliable. However, don’t just throw up your hands in frustration; use this as an opportunity to describe a need for future research based on designing a different method for gathering data.
Lack of prior research studies on the topic -- citing prior research studies forms the basis of your literature review and helps lay a foundation for understanding the research problem you are investigating. Depending on the currency or scope of your research topic, there may be little, if any, prior research on your topic. Before assuming this to be true, though, consult with a librarian! In cases when a librarian has confirmed that there is little or no prior research, you may be required to develop an entirely new research typology [for example, using an exploratory rather than an explanatory research design ]. Note again that discovering a limitation can serve as an important opportunity to identify new gaps in the literature and to describe the need for further research.
Measure used to collect the data -- sometimes it is the case that, after completing your interpretation of the findings, you discover that the way in which you gathered data inhibited your ability to conduct a thorough analysis of the results. For example, you regret not including a specific question in a survey that, in retrospect, could have helped address a particular issue that emerged later in the study. Acknowledge the deficiency by stating a need for future researchers to revise the specific method for gathering data.
Self-reported data -- whether you are relying on pre-existing data or you are conducting a qualitative research study and gathering the data yourself, self-reported data is limited by the fact that it rarely can be independently verified. In other words, you have to the accuracy of what people say, whether in interviews, focus groups, or on questionnaires, at face value. However, self-reported data can contain several potential sources of bias that you should be alert to and note as limitations. These biases become apparent if they are incongruent with data from other sources. These are: (1) selective memory [remembering or not remembering experiences or events that occurred at some point in the past]; (2) telescoping [recalling events that occurred at one time as if they occurred at another time]; (3) attribution [the act of attributing positive events and outcomes to one's own agency, but attributing negative events and outcomes to external forces]; and, (4) exaggeration [the act of representing outcomes or embellishing events as more significant than is actually suggested from other data].

Possible Limitations of the Researcher

Access -- if your study depends on having access to people, organizations, data, or documents and, for whatever reason, access is denied or limited in some way, the reasons for this needs to be described. Also, include an explanation why being denied or limited access did not prevent you from following through on your study.
Longitudinal effects -- unlike your professor, who can literally devote years [even a lifetime] to studying a single topic, the time available to investigate a research problem and to measure change or stability over time is constrained by the due date of your assignment. Be sure to choose a research problem that does not require an excessive amount of time to complete the literature review, apply the methodology, and gather and interpret the results. If you're unsure whether you can complete your research within the confines of the assignment's due date, talk to your professor.
Cultural and other type of bias -- we all have biases, whether we are conscience of them or not. Bias is when a person, place, event, or thing is viewed or shown in a consistently inaccurate way. Bias is usually negative, though one can have a positive bias as well, especially if that bias reflects your reliance on research that only support your hypothesis. When proof-reading your paper, be especially critical in reviewing how you have stated a problem, selected the data to be studied, what may have been omitted, the manner in which you have ordered events, people, or places, how you have chosen to represent a person, place, or thing, to name a phenomenon, or to use possible words with a positive or negative connotation. NOTE : If you detect bias in prior research, it must be acknowledged and you should explain what measures were taken to avoid perpetuating that bias. For example, if a previous study only used boys to examine how music education supports effective math skills, describe how your research expands the study to include girls.
Fluency in a language -- if your research focuses , for example, on measuring the perceived value of after-school tutoring among Mexican-American ESL [English as a Second Language] students and you are not fluent in Spanish, you are limited in being able to read and interpret Spanish language research studies on the topic or to speak with these students in their primary language. This deficiency should be acknowledged.

Structure and Writing Style

If you determine that your study is seriously flawed due to important limitations , such as, an inability to acquire critical data, consider reframing it as an exploratory study intended to lay the groundwork for a more complete research study in the future. Be sure, though, to specifically explain the ways that these flaws can be successfully overcome in a new study.

But, do not use this as an excuse for not developing a thorough research paper! Review the tab in this guide for developing a research topic . If serious limitations exist, it generally indicates a likelihood that your research problem is too narrowly defined or that the issue or event under study is too recent and, thus, very little research has been written about it. If serious limitations do emerge, consult with your professor about possible ways to overcome them or how to revise your study.

When discussing the limitations of your research, be sure to:

Describe each limitation in detailed but concise terms;
Explain why each limitation exists;
Provide the reasons why each limitation could not be overcome using the method(s) chosen to acquire or gather the data [cite to other studies that had similar problems when possible];
Assess the impact of each limitation in relation to the overall findings and conclusions of your study; and,
If appropriate, describe how these limitations could point to the need for further research.

Remember that the method you chose may be the source of a significant limitation that has emerged during your interpretation of the results [for example, you didn't interview a group of people that you later wish you had]. If this is the case, don't panic. Acknowledge it, and explain how applying a different or more robust methodology might address the research problem more effectively in a future study. A underlying goal of scholarly research is not only to show what works, but to demonstrate what doesn't work or what needs further clarification.

Aguinis, Hermam and Jeffrey R. Edwards. “Methodological Wishes for the Next Decade and How to Make Wishes Come True.” Journal of Management Studies 51 (January 2014): 143-174; Brutus, Stéphane et al. "Self-Reported Limitations and Future Directions in Scholarly Reports: Analysis and Recommendations." Journal of Management 39 (January 2013): 48-75; Ioannidis, John P.A. "Limitations are not Properly Acknowledged in the Scientific Literature." Journal of Clinical Epidemiology 60 (2007): 324-329; Pasek, Josh. Writing the Empirical Social Science Research Paper: A Guide for the Perplexed. January 24, 2012. Academia.edu; Structure: How to Structure the Research Limitations Section of Your Dissertation. Dissertations and Theses: An Online Textbook. Laerd.com; What Is an Academic Paper? Institute for Writing Rhetoric. Dartmouth College; Writing the Experimental Report: Methods, Results, and Discussion. The Writing Lab and The OWL. Purdue University.

Writing Tip

Don't Inflate the Importance of Your Findings!

After all the hard work and long hours devoted to writing your research paper, it is easy to get carried away with attributing unwarranted importance to what you’ve done. We all want our academic work to be viewed as excellent and worthy of a good grade, but it is important that you understand and openly acknowledge the limitations of your study. Inflating the importance of your study's findings could be perceived by your readers as an attempt hide its flaws or encourage a biased interpretation of the results. A small measure of humility goes a long way!

Another Writing Tip

Negative Results are Not a Limitation!

Negative evidence refers to findings that unexpectedly challenge rather than support your hypothesis. If you didn't get the results you anticipated, it may mean your hypothesis was incorrect and needs to be reformulated. Or, perhaps you have stumbled onto something unexpected that warrants further study. Moreover, the absence of an effect may be very telling in many situations, particularly in experimental research designs. In any case, your results may very well be of importance to others even though they did not support your hypothesis. Do not fall into the trap of thinking that results contrary to what you expected is a limitation to your study. If you carried out the research well, they are simply your results and only require additional interpretation.

Lewis, George H. and Jonathan F. Lewis. “The Dog in the Night-Time: Negative Evidence in Social Research.” The British Journal of Sociology 31 (December 1980): 544-558.

Yet Another Writing Tip

Sample Size Limitations in Qualitative Research

Sample sizes are typically smaller in qualitative research because, as the study goes on, acquiring more data does not necessarily lead to more information. This is because one occurrence of a piece of data, or a code, is all that is necessary to ensure that it becomes part of the analysis framework. However, it remains true that sample sizes that are too small cannot adequately support claims of having achieved valid conclusions and sample sizes that are too large do not permit the deep, naturalistic, and inductive analysis that defines qualitative inquiry. Determining adequate sample size in qualitative research is ultimately a matter of judgment and experience in evaluating the quality of the information collected against the uses to which it will be applied and the particular research method and purposeful sampling strategy employed. If the sample size is found to be a limitation, it may reflect your judgment about the methodological technique chosen [e.g., single life history study versus focus group interviews] rather than the number of respondents used.

Boddy, Clive Roland. "Sample Size for Qualitative Research." Qualitative Market Research: An International Journal 19 (2016): 426-432; Huberman, A. Michael and Matthew B. Miles. "Data Management and Analysis Methods." In Handbook of Qualitative Research . Norman K. Denzin and Yvonna S. Lincoln, eds. (Thousand Oaks, CA: Sage, 1994), pp. 428-444; Blaikie, Norman. "Confounding Issues Related to Determining Sample Size in Qualitative Research." International Journal of Social Research Methodology 21 (2018): 635-641; Oppong, Steward Harrison. "The Problem of Sampling in qualitative Research." Asian Journal of Management Sciences and Education 2 (2013): 202-210.

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Home » Limitations in Research – Types, Examples and Writing Guide

Limitations in Research – Types, Examples and Writing Guide

Table of Contents

Limitations in Research

Limitations in research refer to the factors that may affect the results, conclusions , and generalizability of a study. These limitations can arise from various sources, such as the design of the study, the sampling methods used, the measurement tools employed, and the limitations of the data analysis techniques.

Types of Limitations in Research

Types of Limitations in Research are as follows:

Sample Size Limitations

This refers to the size of the group of people or subjects that are being studied. If the sample size is too small, then the results may not be representative of the population being studied. This can lead to a lack of generalizability of the results.

Time Limitations

Time limitations can be a constraint on the research process . This could mean that the study is unable to be conducted for a long enough period of time to observe the long-term effects of an intervention, or to collect enough data to draw accurate conclusions.

Selection Bias

This refers to a type of bias that can occur when the selection of participants in a study is not random. This can lead to a biased sample that is not representative of the population being studied.

Confounding Variables

Confounding variables are factors that can influence the outcome of a study, but are not being measured or controlled for. These can lead to inaccurate conclusions or a lack of clarity in the results.

Measurement Error

This refers to inaccuracies in the measurement of variables, such as using a faulty instrument or scale. This can lead to inaccurate results or a lack of validity in the study.

Ethical Limitations

Ethical limitations refer to the ethical constraints placed on research studies. For example, certain studies may not be allowed to be conducted due to ethical concerns, such as studies that involve harm to participants.

Examples of Limitations in Research

Some Examples of Limitations in Research are as follows:

Research Title: “The Effectiveness of Machine Learning Algorithms in Predicting Customer Behavior”

Limitations:

The study only considered a limited number of machine learning algorithms and did not explore the effectiveness of other algorithms.
The study used a specific dataset, which may not be representative of all customer behaviors or demographics.
The study did not consider the potential ethical implications of using machine learning algorithms in predicting customer behavior.

Research Title: “The Impact of Online Learning on Student Performance in Computer Science Courses”

The study was conducted during the COVID-19 pandemic, which may have affected the results due to the unique circumstances of remote learning.
The study only included students from a single university, which may limit the generalizability of the findings to other institutions.
The study did not consider the impact of individual differences, such as prior knowledge or motivation, on student performance in online learning environments.

Research Title: “The Effect of Gamification on User Engagement in Mobile Health Applications”

The study only tested a specific gamification strategy and did not explore the effectiveness of other gamification techniques.
The study relied on self-reported measures of user engagement, which may be subject to social desirability bias or measurement errors.
The study only included a specific demographic group (e.g., young adults) and may not be generalizable to other populations with different preferences or needs.

How to Write Limitations in Research

When writing about the limitations of a research study, it is important to be honest and clear about the potential weaknesses of your work. Here are some tips for writing about limitations in research:

Identify the limitations: Start by identifying the potential limitations of your research. These may include sample size, selection bias, measurement error, or other issues that could affect the validity and reliability of your findings.
Be honest and objective: When describing the limitations of your research, be honest and objective. Do not try to minimize or downplay the limitations, but also do not exaggerate them. Be clear and concise in your description of the limitations.
Provide context: It is important to provide context for the limitations of your research. For example, if your sample size was small, explain why this was the case and how it may have affected your results. Providing context can help readers understand the limitations in a broader context.
Discuss implications : Discuss the implications of the limitations for your research findings. For example, if there was a selection bias in your sample, explain how this may have affected the generalizability of your findings. This can help readers understand the limitations in terms of their impact on the overall validity of your research.
Provide suggestions for future research : Finally, provide suggestions for future research that can address the limitations of your study. This can help readers understand how your research fits into the broader field and can provide a roadmap for future studies.

Purpose of Limitations in Research

There are several purposes of limitations in research. Here are some of the most important ones:

To acknowledge the boundaries of the study : Limitations help to define the scope of the research project and set realistic expectations for the findings. They can help to clarify what the study is not intended to address.
To identify potential sources of bias: Limitations can help researchers identify potential sources of bias in their research design, data collection, or analysis. This can help to improve the validity and reliability of the findings.
To provide opportunities for future research: Limitations can highlight areas for future research and suggest avenues for further exploration. This can help to advance knowledge in a particular field.
To demonstrate transparency and accountability: By acknowledging the limitations of their research, researchers can demonstrate transparency and accountability to their readers, peers, and funders. This can help to build trust and credibility in the research community.
To encourage critical thinking: Limitations can encourage readers to critically evaluate the study’s findings and consider alternative explanations or interpretations. This can help to promote a more nuanced and sophisticated understanding of the topic under investigation.

When to Write Limitations in Research

Limitations should be included in research when they help to provide a more complete understanding of the study’s results and implications. A limitation is any factor that could potentially impact the accuracy, reliability, or generalizability of the study’s findings.

It is important to identify and discuss limitations in research because doing so helps to ensure that the results are interpreted appropriately and that any conclusions drawn are supported by the available evidence. Limitations can also suggest areas for future research, highlight potential biases or confounding factors that may have affected the results, and provide context for the study’s findings.

Generally, limitations should be discussed in the conclusion section of a research paper or thesis, although they may also be mentioned in other sections, such as the introduction or methods. The specific limitations that are discussed will depend on the nature of the study, the research question being investigated, and the data that was collected.

Examples of limitations that might be discussed in research include sample size limitations, data collection methods, the validity and reliability of measures used, and potential biases or confounding factors that could have affected the results. It is important to note that limitations should not be used as a justification for poor research design or methodology, but rather as a way to enhance the understanding and interpretation of the study’s findings.

Importance of Limitations in Research

Here are some reasons why limitations are important in research:

Enhances the credibility of research: Limitations highlight the potential weaknesses and threats to validity, which helps readers to understand the scope and boundaries of the study. This improves the credibility of research by acknowledging its limitations and providing a clear picture of what can and cannot be concluded from the study.
Facilitates replication: By highlighting the limitations, researchers can provide detailed information about the study’s methodology, data collection, and analysis. This information helps other researchers to replicate the study and test the validity of the findings, which enhances the reliability of research.
Guides future research : Limitations provide insights into areas for future research by identifying gaps or areas that require further investigation. This can help researchers to design more comprehensive and effective studies that build on existing knowledge.
Provides a balanced view: Limitations help to provide a balanced view of the research by highlighting both strengths and weaknesses. This ensures that readers have a clear understanding of the study’s limitations and can make informed decisions about the generalizability and applicability of the findings.

Advantages of Limitations in Research

Here are some potential advantages of limitations in research:

Focus : Limitations can help researchers focus their study on a specific area or population, which can make the research more relevant and useful.
Realism : Limitations can make a study more realistic by reflecting the practical constraints and challenges of conducting research in the real world.
Innovation : Limitations can spur researchers to be more innovative and creative in their research design and methodology, as they search for ways to work around the limitations.
Rigor : Limitations can actually increase the rigor and credibility of a study, as researchers are forced to carefully consider the potential sources of bias and error, and address them to the best of their abilities.
Generalizability : Limitations can actually improve the generalizability of a study by ensuring that it is not overly focused on a specific sample or situation, and that the results can be applied more broadly.

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Research Limitations 101 📖

A Plain-Language Explainer (With Practical Examples)

By: Derek Jansen (MBA) | Expert Reviewer: Dr. Eunice Rautenbach | May 2024

Research limitations are one of those things that students tend to avoid digging into, and understandably so. No one likes to critique their own study and point out weaknesses. Nevertheless, being able to understand the limitations of your study – and, just as importantly, the implications thereof – a is a critically important skill.

In this post, we’ll unpack some of the most common research limitations you’re likely to encounter, so that you can approach your project with confidence.

Overview: Research Limitations 101

What are research limitations ?
Access – based limitations
Temporal & financial limitations
Sample & sampling limitations
Design limitations
Researcher limitations
Key takeaways

What (exactly) are “research limitations”?

At the simplest level, research limitations (also referred to as “the limitations of the study”) are the constraints and challenges that will invariably influence your ability to conduct your study and draw reliable conclusions .

Research limitations are inevitable. Absolutely no study is perfect and limitations are an inherent part of any research design. These limitations can stem from a variety of sources , including access to data, methodological choices, and the more mundane constraints of budget and time. So, there’s no use trying to escape them – what matters is that you can recognise them.

Acknowledging and understanding these limitations is crucial, not just for the integrity of your research, but also for your development as a scholar. That probably sounds a bit rich, but realistically, having a strong understanding of the limitations of any given study helps you handle the inevitable obstacles professionally and transparently, which in turn builds trust with your audience and academic peers.

Simply put, recognising and discussing the limitations of your study demonstrates that you know what you’re doing , and that you’ve considered the results of your project within the context of these limitations. In other words, discussing the limitations is a sign of credibility and strength – not weakness. Contrary to the common misconception, highlighting your limitations (or rather, your study’s limitations) will earn you (rather than cost you) marks.

So, with that foundation laid, let’s have a look at some of the most common research limitations you’re likely to encounter – and how to go about managing them as effectively as possible.

Need a helping hand?

research limitations and how to overcome them

Limitation #1: Access To Information

One of the first hurdles you might encounter is limited access to necessary information. For example, you may have trouble getting access to specific literature or niche data sets. This situation can manifest due to several reasons, including paywalls, copyright and licensing issues or language barriers.

To minimise situations like these, it’s useful to try to leverage your university’s resource pool to the greatest extent possible. In practical terms, this means engaging with your university’s librarian and/or potentially utilising interlibrary loans to get access to restricted resources. If this sounds foreign to you, have a chat with your librarian 🙃

In emerging fields or highly specific study areas, you might find that there’s very little existing research (i.e., literature) on your topic. This scenario, while challenging, also offers a unique opportunity to contribute significantly to your field , as it indicates that there’s a significant research gap .

All of that said, be sure to conduct an exhaustive search using a variety of keywords and Boolean operators before assuming that there’s a lack of literature. Also, remember to snowball your literature base . In other words, scan the reference lists of the handful of papers that are directly relevant and then scan those references for more sources. You can also consider using tools like Litmaps and Connected Papers (see video below).

Limitation #2: Time & Money

Almost every researcher will face time and budget constraints at some point. Naturally, these limitations can affect the depth and breadth of your research – but they don’t need to be a death sentence.

Effective planning is crucial to managing both the temporal and financial aspects of your study. In practical terms, utilising tools like Gantt charts can help you visualise and plan your research timeline realistically, thereby reducing the risk of any nasty surprises. Always take a conservative stance when it comes to timelines, especially if you’re new to academic research. As a rule of thumb, things will generally take twice as long as you expect – so, prepare for the worst-case scenario.

If budget is a concern, you might want to consider exploring small research grants or adjusting the scope of your study so that it fits within a realistic budget. Trimming back might sound unattractive, but keep in mind that a smaller, well-planned study can often be more impactful than a larger, poorly planned project.

If you find yourself in a position where you’ve already run out of cash, don’t panic. There’s usually a pivot opportunity hidden somewhere within your project. Engage with your research advisor or faculty to explore potential solutions – don’t make any major changes without first consulting your institution.

Limitation #3: Sample Size & Composition

As we’ve discussed before , the size and representativeness of your sample are crucial , especially in quantitative research where the robustness of your conclusions often depends on these factors. All too often though, students run into issues achieving a sufficient sample size and composition.

To ensure adequacy in terms of your sample size, it’s important to plan for potential dropouts by oversampling from the outset . In other words, if you aim for a final sample size of 100 participants, aim to recruit 120-140 to account for unexpected challenges. If you still find yourself short on participants, consider whether you could complement your dataset with secondary data or data from an adjacent sample – for example, participants from another city or country. That said, be sure to engage with your research advisor before making any changes to your approach.

A related issue that you may run into is sample composition. In other words, you may have trouble securing a random sample that’s representative of your population of interest. In cases like this, you might again want to look at ways to complement your dataset with other sources, but if that’s not possible, it’s not the end of the world. As with all limitations, you’ll just need to recognise this limitation in your final write-up and be sure to interpret your results accordingly. In other words, don’t claim generalisability of your results if your sample isn’t random.

Limitation #4: Methodological Limitations

As we alluded earlier, every methodological choice comes with its own set of limitations . For example, you can’t claim causality if you’re using a descriptive or correlational research design. Similarly, as we saw in the previous example, you can’t claim generalisability if you’re using a non-random sampling approach.

Making good methodological choices is all about understanding (and accepting) the inherent trade-offs . In the vast majority of cases, you won’t be able to adopt the “perfect” methodology – and that’s okay. What’s important is that you select a methodology that aligns with your research aims and research questions , as well as the practical constraints at play (e.g., time, money, equipment access, etc.). Just as importantly, you must recognise and articulate the limitations of your chosen methods, and justify why they were the most suitable, given your specific context.

Limitation #5: Researcher (In)experience

A discussion about research limitations would not be complete without mentioning the researcher (that’s you!). Whether we like to admit it or not, researcher inexperience and personal biases can subtly (and sometimes not so subtly) influence the interpretation and presentation of data within a study. This is especially true when it comes to dissertations and theses , as these are most commonly undertaken by first-time (or relatively fresh) researchers.

When it comes to dealing with this specific limitation, it’s important to remember the adage “ We don’t know what we don’t know ”. In other words, recognise and embrace your (relative) ignorance and subjectivity – and interpret your study’s results within that context . Simply put, don’t be overly confident in drawing conclusions from your study – especially when they contradict existing literature.

Cultivating a culture of reflexivity within your research practices can help reduce subjectivity and keep you a bit more “rooted” in the data. In practical terms, this simply means making an effort to become aware of how your perspectives and experiences may have shaped the research process and outcomes.

As with any new endeavour in life, it’s useful to garner as many outsider perspectives as possible. Of course, your university-assigned research advisor will play a large role in this respect, but it’s also a good idea to seek out feedback and critique from other academics. To this end, you might consider approaching other faculty at your institution, joining an online group, or even working with a private coach .

Your inexperience and personal biases can subtly (but significantly) influence how you interpret your data and draw your conclusions.

Key Takeaways

Understanding and effectively navigating research limitations is key to conducting credible and reliable academic work. By acknowledging and addressing these limitations upfront, you not only enhance the integrity of your research, but also demonstrate your academic maturity and professionalism.

Whether you’re working on a dissertation, thesis or any other type of formal academic research, remember the five most common research limitations and interpret your data while keeping them in mind.

Access to Information (literature and data)
Time and money
Sample size and composition
Research design and methodology
Researcher (in)experience and bias

If you need a hand identifying and mitigating the limitations within your study, check out our 1:1 private coaching service .

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The Scientist University

How to Present a Research Study’s Limitations

All studies have imperfections, but how to present them without diminishing the value of the work can be tricky..

Nathan Ni holds a PhD from Queens University. He is a science editor for The Scientist’s Creative Services Team who strives to better understand and communicate the relationships between health and disease.

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An individual working at a scientific bench in front of a microscope.

Scientists work with many different limitations. First and foremost, they navigate informational limitations, work around knowledge gaps when designing studies, formulating hypotheses, and analyzing data. They also handle technical limitations, making the most of what their hands, equipment, and instruments can achieve. Finally, researchers must also manage logistical limitations. Scientists will often experience sample scarcity, financial issues, or simply be unable to access the technology or materials that they want.

All scientific studies have limitations, and no study is perfect. Researchers should not run from this reality, but engage it directly. It is better to directly address the specific limitations of the work in question, and doing so is actually a way to demonstrate an author’s proficiency and aptitude.

Do: Be Transparent

From a practical perspective, being transparent is the main key to directly addressing the specific limitations of a study. Was there an experiment that the researchers wanted to perform but could not, or a sample that existed that the scientists could not obtain? Was there a piece of knowledge that would explain a question raised by the data presented within the current study? If the answer is yes, the authors should mention this and elaborate upon it within the discussion section.

Asking and addressing these questions demonstrates that the authors have knowledge, understanding, and expertise of the subject area beyond what the study directly investigated. It further demonstrates a solid grasp of the existing literature—which means a solid grasp of what others are doing, what techniques they are using, and what limitations impede their own studies. This information helps the authors contextualize where their study fits within what others have discovered, thereby mitigating the perceived effect of a given limitation on the study’s legitimacy. In essence, this strategy turns limitations, often considered weaknesses, into strengths.

For example, in their 2021 Cell Reports study on macrophage polarization mechanisms, dermatologist Alexander Marneros and colleagues wrote the following. 1

A limitation of studying macrophage polarization in vitro is that this approach only partially captures the tissue microenvironment context in which many different factors affect macrophage polarization. However, it is likely that the identified signaling mechanisms that promote polarization in vitro are also critical for polarization mechanisms that occur in vivo. This is supported by our observation that trametinib and panobinostat inhibited M2-type macrophage polarization not only in vitro but also in skin wounds and laser-induced CNV lesions.

This is a very effective structure. In the first sentence ( yellow ), the authors outlined the limitation. In the next sentence ( green ), they offered a rationalization that mitigates the effect of the limitation. Finally, they provided the evidence ( blue ) for this rationalization, using not just information from the literature, but also data that they obtained in their study specifically for this purpose.

The Do’s and Don’ts of Presenting a Study’s Limitations. Researchers should be transparent, specific, present limitations as future opportunities, and use data or the literature to support rationalizations. They should not be evasive, general, defensive, and downplay limitations without evidence.

Don't: Be Defensive

It can feel natural to avoid talking about a study’s limitations. Scientists may believe that mentioning the drawbacks still present in their study will jeopardize their chances of publication. As such, researchers will sometimes skirt around the issue. They will present “boilerplate faults”—generalized concerns about sample size/diversity and time limitations that all researchers face—rather than honestly discussing their own study. Alternatively, they will describe their limitations in a defensive manner, positioning their problems as something that “could not be helped”—as something beyond what science can currently achieve.

However, their audience can see through this, because they are largely peers who understand and have experienced how modern research works. They can tell the difference between global challenges faced by every scientific study and limitations that are specific to a single study. Avoiding these specific limitations can therefore betray a lack of confidence that the study is good enough to withstand problems stemming from legitimate limitations. As such, researchers should actively engage with the greater scientific implications of the limitations that they face. Indeed, doing this is actually a way to demonstrate an author’s proficiency and aptitude.

In an example, neurogeneticist Nancy Bonini and colleagues, in their publication in Nature , discussed a question raised by their data that they have elected not to directly investigate in this study, writing “ Among the intriguing questions raised by these data is how senescent glia promote LDs in other glia. ” To show both the legitimacy of the question and how seriously they have considered it, the authors provided a comprehensive summary of the literature in the following seven sentences, offering two hypotheses backed by a combined eight different sources. 2 Rather than shying away from a limitation, they attacked it as something to be curious about and to discuss. This is not just a very effective way of demonstrating their expertise, but it frames the limitation as something that, when overcome, will build upon the present study rather than something that negatively affects the legitimacy of their current findings.

Striking the Right Balance

Scientists have to navigate the fine line between acknowledging the limitations of their study while also not diminishing the effect and value of their own work. To be aware of legitimate limitations and properly assess and dissect them shows a profound understanding of a field, where the study fits within that field, and what the rest of the scientific community are doing and what challenges they face.

All studies are parts of a greater whole. Pretending otherwise is a disservice to the scientific community.

Looking for more information on scientific writing? Check out The Scientist’ s TS SciComm section. Looking for some help putting together a manuscript, a figure, a poster, or anything else? The Scientist ’s Scientific Services may have the professional help that you need.

He L, et al. Global characterization of macrophage polarization mechanisms and identification of M2-type polarization inhibitors . Cell Rep . 2021;37(5):109955.
Byrns CN, et al. Senescent glia link mitochondrial dysfunction and lipid accumulation . Nature . 2024.

CPS Online Graduate Studies Research Paper (UNH Manchester Library): Limitations of the Study

Overview of the Research Process for Capstone Projects
Types of Research Design
Selecting a Research Problem
The Title of Your Research Paper
Before You Begin Writing
7 Parts of the Research Paper
Background Information
Quanitative and Qualitative Methods
Qualitative Methods
Quanitative Methods
Resources to Help You With the Literature Review
Non-Textual Elements

Limitations of the Study

Format of Capstone Research Projects at GSC
Editing and Proofreading Your Paper
Acknowledgements
UNH Scholar's Repository

The limitations of the study are those characteristics of design or methodology that impacted or influenced the interpretation of the findings from your research. They are the constraints on generalizability, applications to practice, and/or utility of findings that are the result of the ways in which you initially chose to design the study and/or the method used to establish internal and external validity.

Price, James H. and Judy Murnan. “Research Limitations and the Necessity of Reporting Them.” American Journal of Health Education 35 (2004): 66-67.

Always acknowledge a study's limitations. It is far better that you identify and acknowledge your study’s limitations than to have them pointed out by your professor and be graded down because you appear to have ignored them.

Keep in mind that acknowledgement of a study's limitations is an opportunity to make suggestions for further research. If you do connect your study's limitations to suggestions for further research, be sure to explain the ways in which these unanswered questions may become more focused because of your study.

Acknowledgement of a study's limitations also provides you with an opportunity to demonstrate that you have thought critically about the research problem, understood the relevant literature published about it, and correctly assessed the methods chosen for studying the problem. A key objective of the research process is not only discovering new knowledge but to also confront assumptions and explore what we don't know.

Price, James H. and Judy Murnan. “Research Limitations and the Necessity of Reporting Them.” American Journal of Health Education 35 (2004): 66-67; Structure: How to Structure the Research Limitations Section of Your Dissertation . Dissertations and Theses: An Online Textbook. Laerd.com.

Descriptions of Possible Limitations

Here are examples of limitations related to methodology and the research process you may need to describe and to discuss how they possibly impacted your results. Descriptions of limitations should be stated in the past tense because they were discovered after you completed your research.

Possible Methodological Limitations

Sample size -- the number of the units of analysis you use in your study is dictated by the type of research problem you are investigating. Note that, if your sample size is too small, it will be difficult to find significant relationships from the data, as statistical tests normally require a larger sample size to ensure a representative distribution of the population and to be considered representative of groups of people to whom results will be generalized or transferred. Note that sample size is less relevant in qualitative research.
Lack of available and/or reliable data -- a lack of data or of reliable data will likely require you to limit the scope of your analysis, the size of your sample, or it can be a significant obstacle in finding a trend and a meaningful relationship. You need to not only describe these limitations but to offer reasons why you believe data is missing or is unreliable. However, don’t just throw up your hands in frustration; use this as an opportunity to describe the need for future research.
Lack of prior research studies on the topic -- citing prior research studies forms the basis of your literature review and helps lay a foundation for understanding the research problem you are investigating. Depending on the currency or scope of your research topic, there may be little, if any, prior research on your topic. Before assuming this to be true, though, consult with a librarian. In cases when a librarian has confirmed that there is no prior research, you may be required to develop an entirely new research typology [for example, using an exploratory rather than an explanatory research design]. Note again that discovering a limitation can serve as an important opportunity to identify new gaps in the literature and to describe the need for further research.
Measure used to collect the data -- sometimes it is the case that, after completing your interpretation of the findings, you discover that the way in which you gathered data inhibited your ability to conduct a thorough analysis of the results. For example, you regret not including a specific question in a survey that, in retrospect, could have helped address a particular issue that emerged later in the study. Acknowledge the deficiency by stating a need for future researchers to revise the specific method for gathering data.
Self-reported data -- whether you are relying on pre-existing data or you are conducting a qualitative research study and gathering the data yourself, self-reported data is limited by the fact that it rarely can be independently verified. In other words, you have to take what people say, whether in interviews, focus groups, or on questionnaires, at face value. However, self-reported data can contain several potential sources of bias that you should be alert to and note as limitations. These biases become apparent if they are incongruent with data from other sources. These are: (1) selective memory [remembering or not remembering experiences or events that occurred at some point in the past]; (2) telescoping [recalling events that occurred at one time as if they occurred at another time]; (3) attribution [the act of attributing positive events and outcomes to one's own agency but attributing negative events and outcomes to external forces]; and, (4) exaggeration [the act of representing outcomes or embellishing events as more significant than is actually suggested from other data].

Possible Limitations of the Researcher

Access -- if your study depends on having access to people, organizations, or documents and, for whatever reason, access is denied or limited in some way, the reasons for this need to be described.
Longitudinal effects -- unlike your professor, who can literally devote years [even a lifetime] to studying a single topic, the time available to investigate a research problem and to measure change or stability over time is pretty much constrained by the due date of your assignment. Be sure to choose a research problem that does not require an excessive amount of time to complete the literature review, apply the methodology, and gather and interpret the results. If you're unsure whether you can complete your research within the confines of the assignment's due date, talk to your professor.
Cultural and other type of bias -- we all have biases, whether we are conscience of them or not. Bias is when a person, place, or thing is viewed or shown in a consistently inaccurate way. Bias is usually negative, though one can have a positive bias as well, especially if that bias reflects your reliance on research that only support for your hypothesis. When proof-reading your paper, be especially critical in reviewing how you have stated a problem, selected the data to be studied, what may have been omitted, the manner in which you have ordered events, people, or places, how you have chosen to represent a person, place, or thing, to name a phenomenon, or to use possible words with a positive or negative connotation.

NOTE: If you detect bias in prior research, it must be acknowledged and you should explain what measures were taken to avoid perpetuating that bias.

Fluency in a language -- if your research focuses on measuring the perceived value of after-school tutoring among Mexican-American ESL [English as a Second Language] students, for example, and you are not fluent in Spanish, you are limited in being able to read and interpret Spanish language research studies on the topic. This deficiency should be acknowledged.

Structure and Writing Style

Information about the limitations of your study are generally placed either at the beginning of the discussion section of your paper so the reader knows and understands the limitations before reading the rest of your analysis of the findings, or, the limitations are outlined at the conclusion of the discussion section as an acknowledgement of the need for further study. Statements about a study's limitations should not be buried in the body [middle] of the discussion section unless a limitation is specific to something covered in that part of the paper. If this is the case, though, the limitation should be reiterated at the conclusion of the section. If you determine that your study is seriously flawed due to important limitations, such as, an inability to acquire critical data, consider reframing it as an exploratory study intended to lay the groundwork for a more complete research study in the future. Be sure, though, to specifically explain the ways that these flaws can be successfully overcome in a new study. But, do not use this as an excuse for not developing a thorough research paper! Review the tab in this guide for developing a research topic. If serious limitations exist, it generally indicates a likelihood that your research problem is too narrowly defined or that the issue or event under study is too recent and, thus, very little research has been written about it. If serious limitations do emerge, consult with your professor about possible ways to overcome them or how to revise your study. When discussing the limitations of your research, be sure to: Describe each limitation in detailed but concise terms; Explain why each limitation exists; Provide the reasons why each limitation could not be overcome using the method(s) chosen to acquire or gather the data [cite to other studies that had similar problems when possible]; Assess the impact of each limitation in relation to the overall findings and conclusions of your study; and, If appropriate, describe how these limitations could point to the need for further research. Remember that the method you chose may be the source of a significant limitation that has emerged during your interpretation of the results [for example, you didn't interview a group of people that you later wish you had]. If this is the case, don't panic. Acknowledge it, and explain how applying a different or more robust methodology might address the research problem more effectively in a future study. A underlying goal of scholarly research is not only to show what works, but to demonstrate what doesn't work or what needs further clarification. Aguinis, Hermam and Jeffrey R. Edwards. “Methodological Wishes for the Next Decade and How to Make Wishes Come True.” Journal of Management Studies 51 (January 2014): 143-174; Brutus, Stéphane et al. "Self-Reported Limitations and Future Directions in Scholarly Reports: Analysis and Recommendations." Journal of Management 39 (January 2013): 48-75; Ioannidis, John P.A. "Limitations are not Properly Acknowledged in the Scientific Literature." Journal of Clinical Epidemiology 60 (2007): 324-329; Pasek, Josh. Writing the Empirical Social Science Research Paper: A Guide for the Perplexed. January 24, 2012. Academia.edu; Structure: How to Structure the Research Limitations Section of Your Dissertation. Dissertations and Theses: An Online Textbook. Laerd.com; What Is an Academic Paper? Institute for Writing Rhetoric. Dartmouth College; Writing the Experimental Report: Methods, Results, and Discussion. The Writing Lab and The OWL. Purdue University.

When discussing the limitations of your research, be sure to:

Describe each limitation in detailed but concise terms;
Explain why each limitation exists;
Provide the reasons why each limitation could not be overcome using the method(s) chosen to acquire or gather the data [cite to other studies that had similar problems when possible];
Assess the impact of each limitation in relation to the overall findings and conclusions of your study; and,
If appropriate, describe how these limitations could point to the need for further research.

Aguinis, Hermam and Jeffrey R. Edwards. “Methodological Wishes for the Next Decade and How to Make Wishes Come True.” Journal of Management Studies 51 (January 2014): 143-174; Brutus, Stéphane et al. "Self-Reported Limitations and Future Directions in Scholarly Reports: Analysis and Recommendations." Journal of Management 39 (January 2013): 48-75; Ioannidis, John P.A. "Limitations are not Properly Acknowledged in the Scientific Literature." Journal of Clinical Epidemiology 60 (2007): 324-329; Pasek, Josh. Writing the Empirical Social Science Research Paper: A Guide for the Perplexed . January 24, 2012. Academia.edu; Structure: How to Structure the Research Limitations Section of Your Dissertation . Dissertations and Theses: An Online Textbook. Laerd.com; What Is an Academic Paper? Institute for Writing Rhetoric. Dartmouth College; Writing the Experimental Report: Methods, Results, and Discussion . The Writing Lab and The OWL. Purdue University.

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Perspect Med Educ
v.8(4); 2019 Aug

Limited by our limitations

Paula t. ross.

Medical School, University of Michigan, Ann Arbor, MI USA

Nikki L. Bibler Zaidi

Study limitations represent weaknesses within a research design that may influence outcomes and conclusions of the research. Researchers have an obligation to the academic community to present complete and honest limitations of a presented study. Too often, authors use generic descriptions to describe study limitations. Including redundant or irrelevant limitations is an ineffective use of the already limited word count. A meaningful presentation of study limitations should describe the potential limitation, explain the implication of the limitation, provide possible alternative approaches, and describe steps taken to mitigate the limitation. This includes placing research findings within their proper context to ensure readers do not overemphasize or minimize findings. A more complete presentation will enrich the readers’ understanding of the study’s limitations and support future investigation.

Introduction

Regardless of the format scholarship assumes, from qualitative research to clinical trials, all studies have limitations. Limitations represent weaknesses within the study that may influence outcomes and conclusions of the research. The goal of presenting limitations is to provide meaningful information to the reader; however, too often, limitations in medical education articles are overlooked or reduced to simplistic and minimally relevant themes (e.g., single institution study, use of self-reported data, or small sample size) [ 1 ]. This issue is prominent in other fields of inquiry in medicine as well. For example, despite the clinical implications, medical studies often fail to discuss how limitations could have affected the study findings and interpretations [ 2 ]. Further, observational research often fails to remind readers of the fundamental limitation inherent in the study design, which is the inability to attribute causation [ 3 ]. By reporting generic limitations or omitting them altogether, researchers miss opportunities to fully communicate the relevance of their work, illustrate how their work advances a larger field under study, and suggest potential areas for further investigation.

Goals of presenting limitations

Medical education scholarship should provide empirical evidence that deepens our knowledge and understanding of education [ 4 , 5 ], informs educational practice and process, [ 6 , 7 ] and serves as a forum for educating other researchers [ 8 ]. Providing study limitations is indeed an important part of this scholarly process. Without them, research consumers are pressed to fully grasp the potential exclusion areas or other biases that may affect the results and conclusions provided [ 9 ]. Study limitations should leave the reader thinking about opportunities to engage in prospective improvements [ 9 – 11 ] by presenting gaps in the current research and extant literature, thereby cultivating other researchers’ curiosity and interest in expanding the line of scholarly inquiry [ 9 ].

Presenting study limitations is also an ethical element of scientific inquiry [ 12 ]. It ensures transparency of both the research and the researchers [ 10 , 13 , 14 ], as well as provides transferability [ 15 ] and reproducibility of methods. Presenting limitations also supports proper interpretation and validity of the findings [ 16 ]. A study’s limitations should place research findings within their proper context to ensure readers are fully able to discern the credibility of a study’s conclusion, and can generalize findings appropriately [ 16 ].

Why some authors may fail to present limitations

As Price and Murnan [ 8 ] note, there may be overriding reasons why researchers do not sufficiently report the limitations of their study. For example, authors may not fully understand the importance and implications of their study’s limitations or assume that not discussing them may increase the likelihood of publication. Word limits imposed by journals may also prevent authors from providing thorough descriptions of their study’s limitations [ 17 ]. Still another possible reason for excluding limitations is a diffusion of responsibility in which some authors may incorrectly assume that the journal editor is responsible for identifying limitations. Regardless of reason or intent, researchers have an obligation to the academic community to present complete and honest study limitations.

A guide to presenting limitations

The presentation of limitations should describe the potential limitations, explain the implication of the limitations, provide possible alternative approaches, and describe steps taken to mitigate the limitations. Too often, authors only list the potential limitations, without including these other important elements.

Describe the limitations

When describing limitations authors should identify the limitation type to clearly introduce the limitation and specify the origin of the limitation. This helps to ensure readers are able to interpret and generalize findings appropriately. Here we outline various limitation types that can occur at different stages of the research process.

Study design

Some study limitations originate from conscious choices made by the researcher (also known as delimitations) to narrow the scope of the study [ 1 , 8 , 18 ]. For example, the researcher may have designed the study for a particular age group, sex, race, ethnicity, geographically defined region, or some other attribute that would limit to whom the findings can be generalized. Such delimitations involve conscious exclusionary and inclusionary decisions made during the development of the study plan, which may represent a systematic bias intentionally introduced into the study design or instrument by the researcher [ 8 ]. The clear description and delineation of delimitations and limitations will assist editors and reviewers in understanding any methodological issues.

Data collection

Study limitations can also be introduced during data collection. An unintentional consequence of human subjects research is the potential of the researcher to influence how participants respond to their questions. Even when appropriate methods for sampling have been employed, some studies remain limited by the use of data collected only from participants who decided to enrol in the study (self-selection bias) [ 11 , 19 ]. In some cases, participants may provide biased input by responding to questions they believe are favourable to the researcher rather than their authentic response (social desirability bias) [ 20 – 22 ]. Participants may influence the data collected by changing their behaviour when they are knowingly being observed (Hawthorne effect) [ 23 ]. Researchers—in their role as an observer—may also bias the data they collect by allowing a first impression of the participant to be influenced by a single characteristic or impression of another characteristic either unfavourably (horns effect) or favourably (halo effort) [ 24 ].

Data analysis

Study limitations may arise as a consequence of the type of statistical analysis performed. Some studies may not follow the basic tenets of inferential statistical analyses when they use convenience sampling (i.e. non-probability sampling) rather than employing probability sampling from a target population [ 19 ]. Another limitation that can arise during statistical analyses occurs when studies employ unplanned post-hoc data analyses that were not specified before the initial analysis [ 25 ]. Unplanned post-hoc analysis may lead to statistical relationships that suggest associations but are no more than coincidental findings [ 23 ]. Therefore, when unplanned post-hoc analyses are conducted, this should be clearly stated to allow the reader to make proper interpretation and conclusions—especially when only a subset of the original sample is investigated [ 23 ].

Study results

The limitations of any research study will be rooted in the validity of its results—specifically threats to internal or external validity [ 8 ]. Internal validity refers to reliability or accuracy of the study results [ 26 ], while external validity pertains to the generalizability of results from the study’s sample to the larger, target population [ 8 ].

Examples of threats to internal validity include: effects of events external to the study (history), changes in participants due to time instead of the studied effect (maturation), systematic reduction in participants related to a feature of the study (attrition), changes in participant responses due to repeatedly measuring participants (testing effect), modifications to the instrument (instrumentality) and selecting participants based on extreme scores that will regress towards the mean in repeat tests (regression to the mean) [ 27 ].

Threats to external validity include factors that might inhibit generalizability of results from the study’s sample to the larger, target population [ 8 , 27 ]. External validity is challenged when results from a study cannot be generalized to its larger population or to similar populations in terms of the context, setting, participants and time [ 18 ]. Therefore, limitations should be made transparent in the results to inform research consumers of any known or potentially hidden biases that may have affected the study and prevent generalization beyond the study parameters.

Explain the implication(s) of each limitation

Authors should include the potential impact of the limitations (e.g., likelihood, magnitude) [ 13 ] as well as address specific validity implications of the results and subsequent conclusions [ 16 , 28 ]. For example, self-reported data may lead to inaccuracies (e.g. due to social desirability bias) which threatens internal validity [ 19 ]. Even a researcher’s inappropriate attribution to a characteristic or outcome (e.g., stereotyping) can overemphasize (either positively or negatively) unrelated characteristics or outcomes (halo or horns effect) and impact the internal validity [ 24 ]. Participants’ awareness that they are part of a research study can also influence outcomes (Hawthorne effect) and limit external validity of findings [ 23 ]. External validity may also be threatened should the respondents’ propensity for participation be correlated with the substantive topic of study, as data will be biased and not represent the population of interest (self-selection bias) [ 29 ]. Having this explanation helps readers interpret the results and generalize the applicability of the results for their own setting.

Provide potential alternative approaches and explanations

Often, researchers use other studies’ limitations as the first step in formulating new research questions and shaping the next phase of research. Therefore, it is important for readers to understand why potential alternative approaches (e.g. approaches taken by others exploring similar topics) were not taken. In addition to alternative approaches, authors can also present alternative explanations for their own study’s findings [ 13 ]. This information is valuable coming from the researcher because of the direct, relevant experience and insight gained as they conducted the study. The presentation of alternative approaches represents a major contribution to the scholarly community.

Describe steps taken to minimize each limitation

No research design is perfect and free from explicit and implicit biases; however various methods can be employed to minimize the impact of study limitations. Some suggested steps to mitigate or minimize the limitations mentioned above include using neutral questions, randomized response technique, force choice items, or self-administered questionnaires to reduce respondents’ discomfort when answering sensitive questions (social desirability bias) [ 21 ]; using unobtrusive data collection measures (e.g., use of secondary data) that do not require the researcher to be present (Hawthorne effect) [ 11 , 30 ]; using standardized rubrics and objective assessment forms with clearly defined scoring instructions to minimize researcher bias, or making rater adjustments to assessment scores to account for rater tendencies (halo or horns effect) [ 24 ]; or using existing data or control groups (self-selection bias) [ 11 , 30 ]. When appropriate, researchers should provide sufficient evidence that demonstrates the steps taken to mitigate limitations as part of their study design [ 13 ].

In conclusion, authors may be limiting the impact of their research by neglecting or providing abbreviated and generic limitations. We present several examples of limitations to consider; however, this should not be considered an exhaustive list nor should these examples be added to the growing list of generic and overused limitations. Instead, careful thought should go into presenting limitations after research has concluded and the major findings have been described. Limitations help focus the reader on key findings, therefore it is important to only address the most salient limitations of the study [ 17 , 28 ] related to the specific research problem, not general limitations of most studies [ 1 ]. It is important not to minimize the limitations of study design or results. Rather, results, including their limitations, must help readers draw connections between current research and the extant literature.

The quality and rigor of our research is largely defined by our limitations [ 31 ]. In fact, one of the top reasons reviewers report recommending acceptance of medical education research manuscripts involves limitations—specifically how the study’s interpretation accounts for its limitations [ 32 ]. Therefore, it is not only best for authors to acknowledge their study’s limitations rather than to have them identified by an editor or reviewer, but proper framing and presentation of limitations can actually increase the likelihood of acceptance. Perhaps, these issues could be ameliorated if academic and research organizations adopted policies and/or expectations to guide authors in proper description of limitations.

Educational resources and simple solutions for your research journey

How to Present the Limitations of a Study in Research?

The limitations of the study convey to the reader how and under which conditions your study results will be evaluated. Scientific research involves investigating research topics, both known and unknown, which inherently includes an element of risk. The risk could arise due to human errors, barriers to data gathering, limited availability of resources, and researcher bias. Researchers are encouraged to discuss the limitations of their research to enhance the process of research, as well as to allow readers to gain an understanding of the study’s framework and value.

Limitations of the research are the constraints placed on the ability to generalize from the results and to further describe applications to practice. It is related to the utility value of the findings based on how you initially chose to design the study, the method used to establish internal and external validity, or the result of unanticipated challenges that emerged during the study. Knowing about these limitations and their impact can explain how the limitations of your study can affect the conclusions and thoughts drawn from your research. 1

Table of Contents

What are the limitations of a study

Researchers are probably cautious to acknowledge what the limitations of the research can be for fear of undermining the validity of the research findings. No research can be faultless or cover all possible conditions. These limitations of your research appear probably due to constraints on methodology or research design and influence the interpretation of your research’s ultimate findings. 2 These are limitations on the generalization and usability of findings that emerge from the design of the research and/or the method employed to ensure validity internally and externally. But such limitations of the study can impact the whole study or research paper. However, most researchers prefer not to discuss the different types of limitations in research for fear of decreasing the value of their paper amongst the reviewers or readers.

Importance of limitations of a study

Writing the limitations of the research papers is often assumed to require lots of effort. However, identifying the limitations of the study can help structure the research better. Therefore, do not underestimate the importance of research study limitations. 3

Opportunity to make suggestions for further research. Suggestions for future research and avenues for further exploration can be developed based on the limitations of the study.
Opportunity to demonstrate critical thinking. A key objective of the research process is to discover new knowledge while questioning existing assumptions and exploring what is new in the particular field. Describing the limitation of the research shows that you have critically thought about the research problem, reviewed relevant literature, and correctly assessed the methods chosen for studying the problem.
Demonstrate Subjective learning process. Writing limitations of the research helps to critically evaluate the impact of the said limitations, assess the strength of the research, and consider alternative explanations or interpretations. Subjective evaluation contributes to a more complex and comprehensive knowledge of the issue under study.

Why should I include limitations of research in my paper

All studies have limitations to some extent. Including limitations of the study in your paper demonstrates the researchers’ comprehensive and holistic understanding of the research process and topic. The major advantages are the following:

Understand the study conditions and challenges encountered . It establishes a complete and potentially logical depiction of the research. The boundaries of the study can be established, and realistic expectations for the findings can be set. They can also help to clarify what the study is not intended to address.
Improve the quality and validity of the research findings. Mentioning limitations of the research creates opportunities for the original author and other researchers to undertake future studies to improve the research outcomes.
Transparency and accountability. Including limitations of the research helps maintain mutual integrity and promote further progress in similar studies.
Identify potential bias sources. Identifying the limitations of the study can help researchers identify potential sources of bias in their research design, data collection, or analysis. This can help to improve the validity and reliability of the findings.

Where do I need to add the limitations of the study in my paper

The limitations of your research can be stated at the beginning of the discussion section, which allows the reader to comprehend the limitations of the study prior to reading the rest of your findings or at the end of the discussion section as an acknowledgment of the need for further research.

Types of limitations in research

There are different types of limitations in research that researchers may encounter. These are listed below:

Research Design Limitations : Restrictions on your research or available procedures may affect the research outputs. If the research goals and objectives are too broad, explain how they should be narrowed down to enhance the focus of your study. If there was a selection bias in your sample, explain how this may affect the generalizability of your findings. This can help readers understand the limitations of the study in terms of their impact on the overall validity of your research.
Impact Limitations : Your study might be limited by a strong regional-, national-, or species-based impact or population- or experimental-specific impact. These inherent limitations on impact affect the extendibility and generalizability of the findings.
Data or statistical limitations : Data or statistical limitations in research are extremely common in experimental (such as medicine, physics, and chemistry) or field-based (such as ecology and qualitative clinical research) studies. Sometimes, it is either extremely difficult to acquire sufficient data or gain access to the data. These limitations of the research might also be the result of your study’s design and might result in an incomplete conclusion to your research.

Limitations of study examples

All possible limitations of the study cannot be included in the discussion section of the research paper or dissertation. It will vary greatly depending on the type and nature of the study. These include types of research limitations that are related to methodology and the research process and that of the researcher as well that you need to describe and discuss how they possibly impacted your results.

Common methodological limitations of the study

Limitations of research due to methodological problems are addressed by identifying the potential problem and suggesting ways in which this should have been addressed. Some potential methodological limitations of the study are as follows. 1

Sample size: The sample size 4 is dictated by the type of research problem investigated. If the sample size is too small, finding a significant relationship from the data will be difficult, as statistical tests require a large sample size to ensure a representative population distribution and generalize the study findings.
Lack of available/reliable data: A lack of available/reliable data will limit the scope of your analysis and the size of your sample or present obstacles in finding a trend or meaningful relationship. So, when writing about the limitations of the study, give convincing reasons why you feel data is absent or untrustworthy and highlight the necessity for a future study focused on developing a new data-gathering strategy.
Lack of prior research studies: Citing prior research studies is required to help understand the research problem being investigated. If there is little or no prior research, an exploratory rather than an explanatory research design will be required. Also, discovering the limitations of the study presents an opportunity to identify gaps in the literature and describe the need for additional study.
Measure used to collect the data: Sometimes, the data gathered will be insufficient to conduct a thorough analysis of the results. A limitation of the study example, for instance, is identifying in retrospect that a specific question could have helped address a particular issue that emerged during data analysis. You can acknowledge the limitation of the research by stating the need to revise the specific method for gathering data in the future.
Self-reported data: Self-reported data cannot be independently verified and can contain several potential bias sources, such as selective memory, attribution, and exaggeration. These biases become apparent if they are incongruent with data from other sources.

General limitations of researchers

Limitations related to the researcher can also influence the study outcomes. These should be addressed, and related remedies should be proposed.

Limited access to data : If your study requires access to people, organizations, data, or documents whose access is denied or limited, the reasons need to be described. An additional explanation stating why this limitation of research did not prevent you from following through on your study is also needed.
Time constraints : Researchers might also face challenges in meeting research deadlines due to a lack of timely participant availability or funds, among others. The impacts of time constraints must be acknowledged by mentioning the need for a future study addressing this research problem.
Conflicts due to biased views and personal issues : Differences in culture or personal views can contribute to researcher bias, as they focus only on the results and data that support their main arguments. To avoid this, pay attention to the problem statement and data gathering.

Steps for structuring the limitations section

Limitations are an inherent part of any research study. Issues may vary, ranging from sampling and literature review to methodology and bias. However, there is a structure for identifying these elements, discussing them, and offering insight or alternatives on how the limitations of the study can be mitigated. This enhances the process of the research and helps readers gain a comprehensive understanding of a study’s conditions.

Identify the research constraints : Identify those limitations having the greatest impact on the quality of the research findings and your ability to effectively answer your research questions and/or hypotheses. These include sample size, selection bias, measurement error, or other issues affecting the validity and reliability of your research.
Describe their impact on your research : Reflect on the nature of the identified limitations and justify the choices made during the research to identify the impact of the study’s limitations on the research outcomes. Explanations can be offered if needed, but without being defensive or exaggerating them. Provide context for the limitations of your research to understand them in a broader context. Any specific limitations due to real-world considerations need to be pointed out critically rather than justifying them as done by some other author group or groups.
Mention the opportunity for future investigations : Suggest ways to overcome the limitations of the present study through future research. This can help readers understand how the research fits into the broader context and offer a roadmap for future studies.

Frequently Asked Questions

Should I mention all the limitations of my study in the research report?

Restrict limitations to what is pertinent to the research question under investigation. The specific limitations you include will depend on the nature of the study, the research question investigated, and the data collected.

Can the limitations of a study affect its credibility?

Stating the limitations of the research is considered favorable by editors and peer reviewers. Connecting your study’s limitations with future possible research can help increase the focus of unanswered questions in this area. In addition, admitting limitations openly and validating that they do not affect the main findings of the study increases the credibility of your study. However, if you determine that your study is seriously flawed, explain ways to successfully overcome such flaws in a future study. For example, if your study fails to acquire critical data, consider reframing the research question as an exploratory study to lay the groundwork for more complete research in the future.

How can I mitigate the limitations of my study?

Strategies to minimize limitations of the research should focus on convincing reviewers and readers that the limitations do not affect the conclusions of the study by showing that the methods are appropriate and that the logic is sound. Here are some steps to follow to achieve this:

Use data that are valid.
Use methods that are appropriate and sound logic to draw inferences.
Use adequate statistical methods for drawing inferences from the data that studies with similar limitations have been published before.

Admit limitations openly and, at the same time, show how they do not affect the main conclusions of the study.

Can the limitations of a study impact its publication chances?

Limitations in your research can arise owing to restrictions in methodology or research design. Although this could impact your chances of publishing your research paper, it is critical to explain your study’s limitations to your intended audience. For example, it can explain how your study constraints may impact the results and views generated from your investigation. It also shows that you have researched the flaws of your study and have a thorough understanding of the subject.

How can limitations in research be used for future studies?

The limitations of a study give you an opportunity to offer suggestions for further research. Your study’s limitations, including problems experienced during the study and the additional study perspectives developed, are a great opportunity to take on a new challenge and help advance knowledge in a particular field.

References:

Brutus, S., Aguinis, H., & Wassmer, U. (2013). Self-reported limitations and future directions in scholarly reports: Analysis and recommendations. Journal of Management , 39 (1), 48-75.
Ioannidis, J. P. (2007). Limitations are not properly acknowledged in the scientific literature. Journal of Clinical Epidemiology , 60 (4), 324-329.
Price, J. H., & Murnan, J. (2004). Research limitations and the necessity of reporting them. American Journal of Health Education , 35 (2), 66.
Boddy, C. R. (2016). Sample size for qualitative research. Qualitative Market Research: An International Journal , 19 (4), 426-432.

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What are the limitations in research and how to write them?

Learn about the potential limitations in research and how to appropriately address them in order to deliver honest and ethical research.

It is fairly uncommon for researchers to stumble into the term research limitations when working on their research paper. Limitations in research can arise owing to constraints on design, methods, materials, and so on, and these aspects, unfortunately, may have an influence on your subject’s findings.

In this Mind The Graph’s article, we’ll discuss some recommendations for writing limitations in research , provide examples of various common types of limitations, and suggest how to properly present this information.

What are the limitations in research?

The limitations in research are the constraints in design, methods or even researchers’ limitations that affect and influence the interpretation of your research’s ultimate findings. These are limitations on the generalization and usability of findings that emerge from the design of the research and/or the method employed to ensure validity both internally and externally.

Researchers are usually cautious to acknowledge the limitations of their research in their publications for fear of undermining the research’s scientific validity. No research is faultless or covers every possible angle. As a result, addressing the constraints of your research exhibits honesty and integrity .

Why should include limitations of research in my paper?

Though limitations tackle potential flaws in research, commenting on them at the conclusion of your paper, by demonstrating that you are aware of these limitations and explaining how they impact the conclusions that may be taken from the research, improves your research by disclosing any issues before other researchers or reviewers do .

Additionally, emphasizing research constraints implies that you have thoroughly investigated the ramifications of research shortcomings and have a thorough understanding of your research problem.

Limits exist in any research; being honest about them and explaining them would impress researchers and reviewers more than disregarding them.

Remember that acknowledging a research’s shortcomings offers a chance to provide ideas for future research, but be careful to describe how your study may help to concentrate on these outstanding problems .

Possible limitations examples

Here are some limitations connected to methodology and the research procedure that you may need to explain and discuss in connection to your findings.

Methodological limitations

Sample size.

The number of units of analysis used in your study is determined by the sort of research issue being investigated. It is important to note that if your sample is too small, finding significant connections in the data will be challenging, as statistical tests typically require a larger sample size to ensure a fair representation and this can be limiting.

Lack of available or reliable data

A lack of data or trustworthy data will almost certainly necessitate limiting the scope of your research or the size of your sample, or it can be a substantial impediment to identifying a pattern and a relevant connection.

Lack of prior research on the subject

Citing previous research papers forms the basis of your literature review and aids in comprehending the research subject you are researching. Yet there may be little if any, past research on your issue.

The measure used to collect data

After finishing your analysis of the findings, you realize that the method you used to collect data limited your capacity to undertake a comprehensive evaluation of the findings. Recognize the flaw by mentioning that future researchers should change the specific approach for data collection.

Issues with research samples and selection

Sampling inaccuracies arise when a probability sampling method is employed to choose a sample, but that sample does not accurately represent the overall population or the relevant group. As a result, your study suffers from “sampling bias” or “selection bias.”

Limitations of the research

When your research requires polling certain persons or a specific group, you may have encountered the issue of limited access to these interviewees. Because of the limited access, you may need to reorganize or rearrange your research. In this scenario, explain why access is restricted and ensure that your findings are still trustworthy and valid despite the constraint.

Time constraints

Practical difficulties may limit the amount of time available to explore a research issue and monitor changes as they occur. If time restrictions have any detrimental influence on your research, recognize this impact by expressing the necessity for a future investigation.

Due to their cultural origins or opinions on observed events, researchers may carry biased opinions, which can influence the credibility of a research. Furthermore, researchers may exhibit biases toward data and conclusions that only support their hypotheses or arguments.

The structure of the limitations section

The limitations of your research are usually stated at the beginning of the discussion section of your paper so that the reader is aware of and comprehends the limitations prior to actually reading the rest of your findings, or they are stated at the end of the discussion section as an acknowledgment of the need for further research.

The ideal way is to divide your limitations section into three steps:

1. Identify the research constraints;

2. Describe in great detail how they affect your research;

3. Mention the opportunity for future investigations and give possibilities.

By following this method while addressing the constraints of your research, you will be able to effectively highlight your research’s shortcomings without jeopardizing the quality and integrity of your research.

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21 Research Limitations Examples

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research limitations examples and definition, explained below

Research limitations refer to the potential weaknesses inherent in a study. All studies have limitations of some sort, meaning declaring limitations doesn’t necessarily need to be a bad thing, so long as your declaration of limitations is well thought-out and explained.

Rarely is a study perfect. Researchers have to make trade-offs when developing their studies, which are often based upon practical considerations such as time and monetary constraints, weighing the breadth of participants against the depth of insight, and choosing one methodology or another.

In research, studies can have limitations such as limited scope, researcher subjectivity, and lack of available research tools.

Acknowledging the limitations of your study should be seen as a strength. It demonstrates your willingness for transparency, humility, and submission to the scientific method and can bolster the integrity of the study. It can also inform future research direction.

Typically, scholars will explore the limitations of their study in either their methodology section, their conclusion section, or both.

Research Limitations Examples

Qualitative and quantitative research offer different perspectives and methods in exploring phenomena, each with its own strengths and limitations. So, I’ve split the limitations examples sections into qualitative and quantitative below.

Qualitative Research Limitations

Qualitative research seeks to understand phenomena in-depth and in context. It focuses on the ‘why’ and ‘how’ questions.

It’s often used to explore new or complex issues, and it provides rich, detailed insights into participants’ experiences, behaviors, and attitudes. However, these strengths also create certain limitations, as explained below.

1. Subjectivity

Qualitative research often requires the researcher to interpret subjective data. One researcher may examine a text and identify different themes or concepts as more dominant than others.

Close qualitative readings of texts are necessarily subjective – and while this may be a limitation, qualitative researchers argue this is the best way to deeply understand everything in context.

Suggested Solution and Response: To minimize subjectivity bias, you could consider cross-checking your own readings of themes and data against other scholars’ readings and interpretations. This may involve giving the raw data to a supervisor or colleague and asking them to code the data separately, then coming together to compare and contrast results.

2. Researcher Bias

The concept of researcher bias is related to, but slightly different from, subjectivity.

Researcher bias refers to the perspectives and opinions you bring with you when doing your research.

For example, a researcher who is explicitly of a certain philosophical or political persuasion may bring that persuasion to bear when interpreting data.

In many scholarly traditions, we will attempt to minimize researcher bias through the utilization of clear procedures that are set out in advance or through the use of statistical analysis tools.

However, in other traditions, such as in postmodern feminist research , declaration of bias is expected, and acknowledgment of bias is seen as a positive because, in those traditions, it is believed that bias cannot be eliminated from research, so instead, it is a matter of integrity to present it upfront.

Suggested Solution and Response: Acknowledge the potential for researcher bias and, depending on your theoretical framework , accept this, or identify procedures you have taken to seek a closer approximation to objectivity in your coding and analysis.

3. Generalizability

If you’re struggling to find a limitation to discuss in your own qualitative research study, then this one is for you: all qualitative research, of all persuasions and perspectives, cannot be generalized.

This is a core feature that sets qualitative data and quantitative data apart.

The point of qualitative data is to select case studies and similarly small corpora and dig deep through in-depth analysis and thick description of data.

Often, this will also mean that you have a non-randomized sample size.

While this is a positive – you’re going to get some really deep, contextualized, interesting insights – it also means that the findings may not be generalizable to a larger population that may not be representative of the small group of people in your study.

Suggested Solution and Response: Suggest future studies that take a quantitative approach to the question.

4. The Hawthorne Effect

The Hawthorne effect refers to the phenomenon where research participants change their ‘observed behavior’ when they’re aware that they are being observed.

This effect was first identified by Elton Mayo who conducted studies of the effects of various factors ton workers’ productivity. He noticed that no matter what he did – turning up the lights, turning down the lights, etc. – there was an increase in worker outputs compared to prior to the study taking place.

Mayo realized that the mere act of observing the workers made them work harder – his observation was what was changing behavior.

So, if you’re looking for a potential limitation to name for your observational research study , highlight the possible impact of the Hawthorne effect (and how you could reduce your footprint or visibility in order to decrease its likelihood).

Suggested Solution and Response: Highlight ways you have attempted to reduce your footprint while in the field, and guarantee anonymity to your research participants.

5. Replicability

Quantitative research has a great benefit in that the studies are replicable – a researcher can get a similar sample size, duplicate the variables, and re-test a study. But you can’t do that in qualitative research.

Qualitative research relies heavily on context – a specific case study or specific variables that make a certain instance worthy of analysis. As a result, it’s often difficult to re-enter the same setting with the same variables and repeat the study.

Furthermore, the individual researcher’s interpretation is more influential in qualitative research, meaning even if a new researcher enters an environment and makes observations, their observations may be different because subjectivity comes into play much more. This doesn’t make the research bad necessarily (great insights can be made in qualitative research), but it certainly does demonstrate a weakness of qualitative research.

6. Limited Scope

“Limited scope” is perhaps one of the most common limitations listed by researchers – and while this is often a catch-all way of saying, “well, I’m not studying that in this study”, it’s also a valid point.

No study can explore everything related to a topic. At some point, we have to make decisions about what’s included in the study and what is excluded from the study.

So, you could say that a limitation of your study is that it doesn’t look at an extra variable or concept that’s certainly worthy of study but will have to be explored in your next project because this project has a clearly and narrowly defined goal.

Suggested Solution and Response: Be clear about what’s in and out of the study when writing your research question.

7. Time Constraints

This is also a catch-all claim you can make about your research project: that you would have included more people in the study, looked at more variables, and so on. But you’ve got to submit this thing by the end of next semester! You’ve got time constraints.

And time constraints are a recognized reality in all research.

But this means you’ll need to explain how time has limited your decisions. As with “limited scope”, this may mean that you had to study a smaller group of subjects, limit the amount of time you spent in the field, and so forth.

Suggested Solution and Response: Suggest future studies that will build on your current work, possibly as a PhD project.

8. Resource Intensiveness

Qualitative research can be expensive due to the cost of transcription, the involvement of trained researchers, and potential travel for interviews or observations.

So, resource intensiveness is similar to the time constraints concept. If you don’t have the funds, you have to make decisions about which tools to use, which statistical software to employ, and how many research assistants you can dedicate to the study.

Suggested Solution and Response: Suggest future studies that will gain more funding on the back of this ‘ exploratory study ‘.

9. Coding Difficulties

Data analysis in qualitative research often involves coding, which can be subjective and complex, especially when dealing with ambiguous or contradicting data.

After naming this as a limitation in your research, it’s important to explain how you’ve attempted to address this. Some ways to ‘limit the limitation’ include:

Triangulation: Have 2 other researchers code the data as well and cross-check your results with theirs to identify outliers that may need to be re-examined, debated with the other researchers, or removed altogether.
Procedure: Use a clear coding procedure to demonstrate reliability in your coding process. I personally use the thematic network analysis method outlined in this academic article by Attride-Stirling (2001).

Suggested Solution and Response: Triangulate your coding findings with colleagues, and follow a thematic network analysis procedure.

10. Risk of Non-Responsiveness

There is always a risk in research that research participants will be unwilling or uncomfortable sharing their genuine thoughts and feelings in the study.

This is particularly true when you’re conducting research on sensitive topics, politicized topics, or topics where the participant is expressing vulnerability .

This is similar to the Hawthorne effect (aka participant bias), where participants change their behaviors in your presence; but it goes a step further, where participants actively hide their true thoughts and feelings from you.

Suggested Solution and Response: One way to manage this is to try to include a wider group of people with the expectation that there will be non-responsiveness from some participants.

11. Risk of Attrition

Attrition refers to the process of losing research participants throughout the study.

This occurs most commonly in longitudinal studies , where a researcher must return to conduct their analysis over spaced periods of time, often over a period of years.

Things happen to people over time – they move overseas, their life experiences change, they get sick, change their minds, and even die. The more time that passes, the greater the risk of attrition.

Suggested Solution and Response: One way to manage this is to try to include a wider group of people with the expectation that there will be attrition over time.

12. Difficulty in Maintaining Confidentiality and Anonymity

Given the detailed nature of qualitative data , ensuring participant anonymity can be challenging.

If you have a sensitive topic in a specific case study, even anonymizing research participants sometimes isn’t enough. People might be able to induce who you’re talking about.

Sometimes, this will mean you have to exclude some interesting data that you collected from your final report. Confidentiality and anonymity come before your findings in research ethics – and this is a necessary limiting factor.

Suggested Solution and Response: Highlight the efforts you have taken to anonymize data, and accept that confidentiality and accountability place extremely important constraints on academic research.

13. Difficulty in Finding Research Participants

A study that looks at a very specific phenomenon or even a specific set of cases within a phenomenon means that the pool of potential research participants can be very low.

Compile on top of this the fact that many people you approach may choose not to participate, and you could end up with a very small corpus of subjects to explore. This may limit your ability to make complete findings, even in a quantitative sense.

You may need to therefore limit your research question and objectives to something more realistic.

Suggested Solution and Response: Highlight that this is going to limit the study’s generalizability significantly.

14. Ethical Limitations

Ethical limitations refer to the things you cannot do based on ethical concerns identified either by yourself or your institution’s ethics review board.

This might include threats to the physical or psychological well-being of your research subjects, the potential of releasing data that could harm a person’s reputation, and so on.

Furthermore, even if your study follows all expected standards of ethics, you still, as an ethical researcher, need to allow a research participant to pull out at any point in time, after which you cannot use their data, which demonstrates an overlap between ethical constraints and participant attrition.

Suggested Solution and Response: Highlight that these ethical limitations are inevitable but important to sustain the integrity of the research.

For more on Qualitative Research, Explore my Qualitative Research Guide

Quantitative Research Limitations

Quantitative research focuses on quantifiable data and statistical, mathematical, or computational techniques. It’s often used to test hypotheses, assess relationships and causality, and generalize findings across larger populations.

Quantitative research is widely respected for its ability to provide reliable, measurable, and generalizable data (if done well!). Its structured methodology has strengths over qualitative research, such as the fact it allows for replication of the study, which underpins the validity of the research.

However, this approach is not without it limitations, explained below.

1. Over-Simplification

Quantitative research is powerful because it allows you to measure and analyze data in a systematic and standardized way. However, one of its limitations is that it can sometimes simplify complex phenomena or situations.

In other words, it might miss the subtleties or nuances of the research subject.

For example, if you’re studying why people choose a particular diet, a quantitative study might identify factors like age, income, or health status. But it might miss other aspects, such as cultural influences or personal beliefs, that can also significantly impact dietary choices.

When writing about this limitation, you can say that your quantitative approach, while providing precise measurements and comparisons, may not capture the full complexity of your subjects of study.

Suggested Solution and Response: Suggest a follow-up case study using the same research participants in order to gain additional context and depth.

2. Lack of Context

Another potential issue with quantitative research is that it often focuses on numbers and statistics at the expense of context or qualitative information.

Let’s say you’re studying the effect of classroom size on student performance. You might find that students in smaller classes generally perform better. However, this doesn’t take into account other variables, like teaching style , student motivation, or family support.

When describing this limitation, you might say, “Although our research provides important insights into the relationship between class size and student performance, it does not incorporate the impact of other potentially influential variables. Future research could benefit from a mixed-methods approach that combines quantitative analysis with qualitative insights.”

3. Applicability to Real-World Settings

Oftentimes, experimental research takes place in controlled environments to limit the influence of outside factors.

This control is great for isolation and understanding the specific phenomenon but can limit the applicability or “external validity” of the research to real-world settings.

For example, if you conduct a lab experiment to see how sleep deprivation impacts cognitive performance, the sterile, controlled lab environment might not reflect real-world conditions where people are dealing with multiple stressors.

Therefore, when explaining the limitations of your quantitative study in your methodology section, you could state:

“While our findings provide valuable information about [topic], the controlled conditions of the experiment may not accurately represent real-world scenarios where extraneous variables will exist. As such, the direct applicability of our results to broader contexts may be limited.”

Suggested Solution and Response: Suggest future studies that will engage in real-world observational research, such as ethnographic research.

4. Limited Flexibility

Once a quantitative study is underway, it can be challenging to make changes to it. This is because, unlike in grounded research, you’re putting in place your study in advance, and you can’t make changes part-way through.

Your study design, data collection methods, and analysis techniques need to be decided upon before you start collecting data.

For example, if you are conducting a survey on the impact of social media on teenage mental health, and halfway through, you realize that you should have included a question about their screen time, it’s generally too late to add it.

When discussing this limitation, you could write something like, “The structured nature of our quantitative approach allows for consistent data collection and analysis but also limits our flexibility to adapt and modify the research process in response to emerging insights and ideas.”

Suggested Solution and Response: Suggest future studies that will use mixed-methods or qualitative research methods to gain additional depth of insight.

5. Risk of Survey Error

Surveys are a common tool in quantitative research, but they carry risks of error.

There can be measurement errors (if a question is misunderstood), coverage errors (if some groups aren’t adequately represented), non-response errors (if certain people don’t respond), and sampling errors (if your sample isn’t representative of the population).

For instance, if you’re surveying college students about their study habits , but only daytime students respond because you conduct the survey during the day, your results will be skewed.

In discussing this limitation, you might say, “Despite our best efforts to develop a comprehensive survey, there remains a risk of survey error, including measurement, coverage, non-response, and sampling errors. These could potentially impact the reliability and generalizability of our findings.”

Suggested Solution and Response: Suggest future studies that will use other survey tools to compare and contrast results.

6. Limited Ability to Probe Answers

With quantitative research, you typically can’t ask follow-up questions or delve deeper into participants’ responses like you could in a qualitative interview.

For instance, imagine you are surveying 500 students about study habits in a questionnaire. A respondent might indicate that they study for two hours each night. You might want to follow up by asking them to elaborate on what those study sessions involve or how effective they feel their habits are.

However, quantitative research generally disallows this in the way a qualitative semi-structured interview could.

When discussing this limitation, you might write, “Given the structured nature of our survey, our ability to probe deeper into individual responses is limited. This means we may not fully understand the context or reasoning behind the responses, potentially limiting the depth of our findings.”

Suggested Solution and Response: Suggest future studies that engage in mixed-method or qualitative methodologies to address the issue from another angle.

7. Reliance on Instruments for Data Collection

In quantitative research, the collection of data heavily relies on instruments like questionnaires, surveys, or machines.

The limitation here is that the data you get is only as good as the instrument you’re using. If the instrument isn’t designed or calibrated well, your data can be flawed.

For instance, if you’re using a questionnaire to study customer satisfaction and the questions are vague, confusing, or biased, the responses may not accurately reflect the customers’ true feelings.

When discussing this limitation, you could say, “Our study depends on the use of questionnaires for data collection. Although we have put significant effort into designing and testing the instrument, it’s possible that inaccuracies or misunderstandings could potentially affect the validity of the data collected.”

Suggested Solution and Response: Suggest future studies that will use different instruments but examine the same variables to triangulate results.

8. Time and Resource Constraints (Specific to Quantitative Research)

Quantitative research can be time-consuming and resource-intensive, especially when dealing with large samples.

It often involves systematic sampling, rigorous design, and sometimes complex statistical analysis.

If resources and time are limited, it can restrict the scale of your research, the techniques you can employ, or the extent of your data analysis.

For example, you may want to conduct a nationwide survey on public opinion about a certain policy. However, due to limited resources, you might only be able to survey people in one city.

When writing about this limitation, you could say, “Given the scope of our research and the resources available, we are limited to conducting our survey within one city, which may not fully represent the nationwide public opinion. Hence, the generalizability of the results may be limited.”

Suggested Solution and Response: Suggest future studies that will have more funding or longer timeframes.

How to Discuss Your Research Limitations

1. in your research proposal and methodology section.

In the research proposal, which will become the methodology section of your dissertation, I would recommend taking the four following steps, in order:

Be Explicit about your Scope – If you limit the scope of your study in your research question, aims, and objectives, then you can set yourself up well later in the methodology to say that certain questions are “outside the scope of the study.” For example, you may identify the fact that the study doesn’t address a certain variable, but you can follow up by stating that the research question is specifically focused on the variable that you are examining, so this limitation would need to be looked at in future studies.
Acknowledge the Limitation – Acknowledging the limitations of your study demonstrates reflexivity and humility and can make your research more reliable and valid. It also pre-empts questions the people grading your paper may have, so instead of them down-grading you for your limitations; they will congratulate you on explaining the limitations and how you have addressed them!
Explain your Decisions – You may have chosen your approach (despite its limitations) for a very specific reason. This might be because your approach remains, on balance, the best one to answer your research question. Or, it might be because of time and monetary constraints that are outside of your control.
Highlight the Strengths of your Approach – Conclude your limitations section by strongly demonstrating that, despite limitations, you’ve worked hard to minimize the effects of the limitations and that you have chosen your specific approach and methodology because it’s also got some terrific strengths. Name the strengths.

Overall, you’ll want to acknowledge your own limitations but also explain that the limitations don’t detract from the value of your study as it stands.

2. In the Conclusion Section or Chapter

In the conclusion of your study, it is generally expected that you return to a discussion of the study’s limitations. Here, I recommend the following steps:

Acknowledge issues faced – After completing your study, you will be increasingly aware of issues you may have faced that, if you re-did the study, you may have addressed earlier in order to avoid those issues. Acknowledge these issues as limitations, and frame them as recommendations for subsequent studies.
Suggest further research – Scholarly research aims to fill gaps in the current literature and knowledge. Having established your expertise through your study, suggest lines of inquiry for future researchers. You could state that your study had certain limitations, and “future studies” can address those limitations.
Suggest a mixed methods approach – Qualitative and quantitative research each have pros and cons. So, note those ‘cons’ of your approach, then say the next study should approach the topic using the opposite methodology or could approach it using a mixed-methods approach that could achieve the benefits of quantitative studies with the nuanced insights of associated qualitative insights as part of an in-study case-study.

Overall, be clear about both your limitations and how those limitations can inform future studies.

In sum, each type of research method has its own strengths and limitations. Qualitative research excels in exploring depth, context, and complexity, while quantitative research excels in examining breadth, generalizability, and quantifiable measures. Despite their individual limitations, each method contributes unique and valuable insights, and researchers often use them together to provide a more comprehensive understanding of the phenomenon being studied.

Attride-Stirling, J. (2001). Thematic networks: an analytic tool for qualitative research. Qualitative research , 1 (3), 385-405. ( Source )

Atkinson, P., Delamont, S., Cernat, A., Sakshaug, J., & Williams, R. A. (2021). SAGE research methods foundations . London: Sage Publications.

Clark, T., Foster, L., Bryman, A., & Sloan, L. (2021). Bryman’s social research methods . Oxford: Oxford University Press.

Köhler, T., Smith, A., & Bhakoo, V. (2022). Templates in qualitative research methods: Origins, limitations, and new directions. Organizational Research Methods , 25 (2), 183-210. ( Source )

Lenger, A. (2019). The rejection of qualitative research methods in economics. Journal of Economic Issues , 53 (4), 946-965. ( Source )

Taherdoost, H. (2022). What are different research approaches? Comprehensive review of qualitative, quantitative, and mixed method research, their applications, types, and limitations. Journal of Management Science & Engineering Research , 5 (1), 53-63. ( Source )

Walliman, N. (2021). Research methods: The basics . New York: Routledge.

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Writing Limitations of Research Study — 4 Reasons Why It Is Important!

It is not unusual for researchers to come across the term limitations of research during their academic paper writing. More often this is interpreted as something terrible. However, when it comes to research study, limitations can help structure the research study better. Therefore, do not underestimate significance of limitations of research study.

Allow us to take you through the context of how to evaluate the limits of your research and conclude an impactful relevance to your results.

Table of Contents

What Are the Limitations of a Research Study?

Every research has its limit and these limitations arise due to restrictions in methodology or research design. This could impact your entire research or the research paper you wish to publish. Unfortunately, most researchers choose not to discuss their limitations of research fearing it will affect the value of their article in the eyes of readers.

However, it is very important to discuss your study limitations and show it to your target audience (other researchers, journal editors, peer reviewers etc.). It is very important that you provide an explanation of how your research limitations may affect the conclusions and opinions drawn from your research. Moreover, when as an author you state the limitations of research, it shows that you have investigated all the weaknesses of your study and have a deep understanding of the subject. Being honest could impress your readers and mark your study as a sincere effort in research.

Why and Where Should You Include the Research Limitations?

The main goal of your research is to address your research objectives. Conduct experiments, get results and explain those results, and finally justify your research question . It is best to mention the limitations of research in the discussion paragraph of your research article.

At the very beginning of this paragraph, immediately after highlighting the strengths of the research methodology, you should write down your limitations. You can discuss specific points from your research limitations as suggestions for further research in the conclusion of your thesis.

1. Common Limitations of the Researchers

Limitations that are related to the researcher must be mentioned. This will help you gain transparency with your readers. Furthermore, you could provide suggestions on decreasing these limitations in you and your future studies.

2. Limited Access to Information

Your work may involve some institutions and individuals in research, and sometimes you may have problems accessing these institutions. Therefore, you need to redesign and rewrite your work. You must explain your readers the reason for limited access.

3. Limited Time

All researchers are bound by their deadlines when it comes to completing their studies. Sometimes, time constraints can affect your research negatively. However, the best practice is to acknowledge it and mention a requirement for future study to solve the research problem in a better way.

4. Conflict over Biased Views and Personal Issues

Biased views can affect the research. In fact, researchers end up choosing only those results and data that support their main argument, keeping aside the other loose ends of the research.

Types of Limitations of Research

Before beginning your research study, know that there are certain limitations to what you are testing or possible research results. There are different types that researchers may encounter, and they all have unique characteristics, such as:

1. Research Design Limitations

Certain restrictions on your research or available procedures may affect your final results or research outputs. You may have formulated research goals and objectives too broadly. However, this can help you understand how you can narrow down the formulation of research goals and objectives, thereby increasing the focus of your study.

2. Impact Limitations

Even if your research has excellent statistics and a strong design, it can suffer from the influence of the following factors:

Presence of increasing findings as researched
Being population specific
A strong regional focus.

3. Data or statistical limitations

In some cases, it is impossible to collect sufficient data for research or very difficult to get access to the data. This could lead to incomplete conclusion to your study. Moreover, this insufficiency in data could be the outcome of your study design. The unclear, shabby research outline could produce more problems in interpreting your findings.

How to Correctly Structure Your Research Limitations?

There are strict guidelines for narrowing down research questions, wherein you could justify and explain potential weaknesses of your academic paper. You could go through these basic steps to get a well-structured clarity of research limitations:

Declare that you wish to identify your limitations of research and explain their importance,
Provide the necessary depth, explain their nature, and justify your study choices.
Write how you are suggesting that it is possible to overcome them in the future.

In this section, your readers will see that you are aware of the potential weaknesses in your business, understand them and offer effective solutions, and it will positively strengthen your article as you clarify all limitations of research to your target audience.

Know that you cannot be perfect and there is no individual without flaws. You could use the limitations of research as a great opportunity to take on a new challenge and improve the future of research. In a typical academic paper, research limitations may relate to:

1. Formulating your goals and objectives

If you formulate goals and objectives too broadly, your work will have some shortcomings. In this case, specify effective methods or ways to narrow down the formula of goals and aim to increase your level of study focus.

2. Application of your data collection methods in research

If you do not have experience in primary data collection, there is a risk that there will be flaws in the implementation of your methods. It is necessary to accept this, and learn and educate yourself to understand data collection methods.

3. Sample sizes

This depends on the nature of problem you choose. Sample size is of a greater importance in quantitative studies as opposed to qualitative ones. If your sample size is too small, statistical tests cannot identify significant relationships or connections within a given data set.

You could point out that other researchers should base the same study on a larger sample size to get more accurate results.

4. The absence of previous studies in the field you have chosen

Writing a literature review is an important step in any scientific study because it helps researchers determine the scope of current work in the chosen field. It is a major foundation for any researcher who must use them to achieve a set of specific goals or objectives.

However, if you are focused on the most current and evolving research problem or a very narrow research problem, there may be very little prior research on your topic. For example, if you chose to explore the role of Bitcoin as the currency of the future, you may not find tons of scientific papers addressing the research problem as Bitcoins are only a new phenomenon.

It is important that you learn to identify research limitations examples at each step. Whatever field you choose, feel free to add the shortcoming of your work. This is mainly because you do not have many years of experience writing scientific papers or completing complex work. Therefore, the depth and scope of your discussions may be compromised at different levels compared to academics with a lot of expertise. Include specific points from limitations of research. Use them as suggestions for the future.

Have you ever faced a challenge of writing the limitations of research study in your paper? How did you overcome it? What ways did you follow? Were they beneficial? Let us know in the comments below!

Frequently Asked Questions

Setting limitations in our study helps to clarify the outcomes drawn from our research and enhance understanding of the subject. Moreover, it shows that the author has investigated all the weaknesses in the study.

Scope is the range and limitations of a research project which are set to define the boundaries of a project. Limitations are the impacts on the overall study due to the constraints on the research design.

Limitation in research is an impact of a constraint on the research design in the overall study. They are the flaws or weaknesses in the study, which may influence the outcome of the research.

1. Limitations in research can be written as follows: Formulate your goals and objectives 2. Analyze the chosen data collection method and the sample sizes 3. Identify your limitations of research and explain their importance 4. Provide the necessary depth, explain their nature, and justify your study choices 5. Write how you are suggesting that it is possible to overcome them in the future

Excellent article ,,,it has helped me big

This is very helpful information. It has given me an insight on how to go about my study limitations.

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the topic is well covered

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Limitations of the Study – How to Write & Examples

What are the limitations of a study?

The limitations of a study are the elements of methodology or study design that impact the interpretation of your research results. The limitations essentially detail any flaws or shortcomings in your study. Study limitations can exist due to constraints on research design, methodology, materials, etc., and these factors may impact the findings of your study. However, researchers are often reluctant to discuss the limitations of their study in their papers, feeling that bringing up limitations may undermine its research value in the eyes of readers and reviewers.

In spite of the impact it might have (and perhaps because of it) you should clearly acknowledge any limitations in your research paper in order to show readers—whether journal editors, other researchers, or the general public—that you are aware of these limitations and to explain how they affect the conclusions that can be drawn from the research.

In this article, we provide some guidelines for writing about research limitations, show examples of some frequently seen study limitations, and recommend techniques for presenting this information. And after you have finished drafting and have received manuscript editing for your work, you still might want to follow this up with academic editing before submitting your work to your target journal.

Why do I need to include limitations of research in my paper?

Although limitations address the potential weaknesses of a study, writing about them toward the end of your paper actually strengthens your study by identifying any problems before other researchers or reviewers find them.

Furthermore, pointing out study limitations shows that you’ve considered the impact of research weakness thoroughly and have an in-depth understanding of your research topic. Since all studies face limitations, being honest and detailing these limitations will impress researchers and reviewers more than ignoring them.

limitations of the study examples, brick wall with blue sky

Where should I put the limitations of the study in my paper?

Some limitations might be evident to researchers before the start of the study, while others might become clear while you are conducting the research. Whether these limitations are anticipated or not, and whether they are due to research design or to methodology, they should be clearly identified and discussed in the discussion section —the final section of your paper. Most journals now require you to include a discussion of potential limitations of your work, and many journals now ask you to place this “limitations section” at the very end of your article.

Some journals ask you to also discuss the strengths of your work in this section, and some allow you to freely choose where to include that information in your discussion section—make sure to always check the author instructions of your target journal before you finalize a manuscript and submit it for peer review .

Limitations of the Study Examples

There are several reasons why limitations of research might exist. The two main categories of limitations are those that result from the methodology and those that result from issues with the researcher(s).

Common Methodological Limitations of Studies

Limitations of research due to methodological problems can be addressed by clearly and directly identifying the potential problem and suggesting ways in which this could have been addressed—and SHOULD be addressed in future studies. The following are some major potential methodological issues that can impact the conclusions researchers can draw from the research.

Issues with research samples and selection

Sampling errors occur when a probability sampling method is used to select a sample, but that sample does not reflect the general population or appropriate population concerned. This results in limitations of your study known as “sample bias” or “selection bias.”

For example, if you conducted a survey to obtain your research results, your samples (participants) were asked to respond to the survey questions. However, you might have had limited ability to gain access to the appropriate type or geographic scope of participants. In this case, the people who responded to your survey questions may not truly be a random sample.

Insufficient sample size for statistical measurements

When conducting a study, it is important to have a sufficient sample size in order to draw valid conclusions. The larger the sample, the more precise your results will be. If your sample size is too small, it will be difficult to identify significant relationships in the data.

Normally, statistical tests require a larger sample size to ensure that the sample is considered representative of a population and that the statistical result can be generalized to a larger population. It is a good idea to understand how to choose an appropriate sample size before you conduct your research by using scientific calculation tools—in fact, many journals now require such estimation to be included in every manuscript that is sent out for review.

Lack of previous research studies on the topic

Citing and referencing prior research studies constitutes the basis of the literature review for your thesis or study, and these prior studies provide the theoretical foundations for the research question you are investigating. However, depending on the scope of your research topic, prior research studies that are relevant to your thesis might be limited.

When there is very little or no prior research on a specific topic, you may need to develop an entirely new research typology. In this case, discovering a limitation can be considered an important opportunity to identify literature gaps and to present the need for further development in the area of study.

Methods/instruments/techniques used to collect the data

After you complete your analysis of the research findings (in the discussion section), you might realize that the manner in which you have collected the data or the ways in which you have measured variables has limited your ability to conduct a thorough analysis of the results.

For example, you might realize that you should have addressed your survey questions from another viable perspective, or that you were not able to include an important question in the survey. In these cases, you should acknowledge the deficiency or deficiencies by stating a need for future researchers to revise their specific methods for collecting data that includes these missing elements.

Common Limitations of the Researcher(s)

Study limitations that arise from situations relating to the researcher or researchers (whether the direct fault of the individuals or not) should also be addressed and dealt with, and remedies to decrease these limitations—both hypothetically in your study, and practically in future studies—should be proposed.

Limited access to data

If your research involved surveying certain people or organizations, you might have faced the problem of having limited access to these respondents. Due to this limited access, you might need to redesign or restructure your research in a different way. In this case, explain the reasons for limited access and be sure that your finding is still reliable and valid despite this limitation.

Time constraints

Just as students have deadlines to turn in their class papers, academic researchers might also have to meet deadlines for submitting a manuscript to a journal or face other time constraints related to their research (e.g., participants are only available during a certain period; funding runs out; collaborators move to a new institution). The time available to study a research problem and to measure change over time might be constrained by such practical issues. If time constraints negatively impacted your study in any way, acknowledge this impact by mentioning a need for a future study (e.g., a longitudinal study) to answer this research problem.

Conflicts arising from cultural bias and other personal issues

Researchers might hold biased views due to their cultural backgrounds or perspectives of certain phenomena, and this can affect a study’s legitimacy. Also, it is possible that researchers will have biases toward data and results that only support their hypotheses or arguments. In order to avoid these problems, the author(s) of a study should examine whether the way the research problem was stated and the data-gathering process was carried out appropriately.

Steps for Organizing Your Study Limitations Section

When you discuss the limitations of your study, don’t simply list and describe your limitations—explain how these limitations have influenced your research findings. There might be multiple limitations in your study, but you only need to point out and explain those that directly relate to and impact how you address your research questions.

We suggest that you divide your limitations section into three steps: (1) identify the study limitations; (2) explain how they impact your study in detail; and (3) propose a direction for future studies and present alternatives. By following this sequence when discussing your study’s limitations, you will be able to clearly demonstrate your study’s weakness without undermining the quality and integrity of your research.

Step 1. Identify the limitation(s) of the study

This part should comprise around 10%-20% of your discussion of study limitations.

The first step is to identify the particular limitation(s) that affected your study. There are many possible limitations of research that can affect your study, but you don’t need to write a long review of all possible study limitations. A 200-500 word critique is an appropriate length for a research limitations section. In the beginning of this section, identify what limitations your study has faced and how important these limitations are.

You only need to identify limitations that had the greatest potential impact on: (1) the quality of your findings, and (2) your ability to answer your research question.

Step 2. Explain these study limitations in detail

This part should comprise around 60-70% of your discussion of limitations.

After identifying your research limitations, it’s time to explain the nature of the limitations and how they potentially impacted your study. For example, when you conduct quantitative research, a lack of probability sampling is an important issue that you should mention. On the other hand, when you conduct qualitative research, the inability to generalize the research findings could be an issue that deserves mention.

Explain the role these limitations played on the results and implications of the research and justify the choice you made in using this “limiting” methodology or other action in your research. Also, make sure that these limitations didn’t undermine the quality of your dissertation .

Step 3. Propose a direction for future studies and present alternatives (optional)

This part should comprise around 10-20% of your discussion of limitations.

After acknowledging the limitations of the research, you need to discuss some possible ways to overcome these limitations in future studies. One way to do this is to present alternative methodologies and ways to avoid issues with, or “fill in the gaps of” the limitations of this study you have presented. Discuss both the pros and cons of these alternatives and clearly explain why researchers should choose these approaches.

Make sure you are current on approaches used by prior studies and the impacts they have had on their findings. Cite review articles or scientific bodies that have recommended these approaches and why. This might be evidence in support of the approach you chose, or it might be the reason you consider your choices to be included as limitations. This process can act as a justification for your approach and a defense of your decision to take it while acknowledging the feasibility of other approaches.

P hrases and Tips for Introducing Your Study Limitations in the Discussion Section

The following phrases are frequently used to introduce the limitations of the study:

“There may be some possible limitations in this study.”
“The findings of this study have to be seen in light of some limitations.”
“The first is the…The second limitation concerns the…”
“The empirical results reported herein should be considered in the light of some limitations.”
“This research, however, is subject to several limitations.”
“The primary limitation to the generalization of these results is…”
“Nonetheless, these results must be interpreted with caution and a number of limitations should be borne in mind.”
“As with the majority of studies, the design of the current study is subject to limitations.”
“There are two major limitations in this study that could be addressed in future research. First, the study focused on …. Second ….”

For more articles on research writing and the journal submissions and publication process, visit Wordvice’s Academic Resources page.

And be sure to receive professional English editing and proofreading services , including paper editing services , for your journal manuscript before submitting it to journal editors.

Wordvice Resources

Proofreading & Editing Guide

Writing the Results Section for a Research Paper

How to Write a Literature Review

Research Writing Tips: How to Draft a Powerful Discussion Section

How to Captivate Journal Readers with a Strong Introduction

Tips That Will Make Your Abstract a Success!

APA In-Text Citation Guide for Research Writing

Additional Resources

Diving Deeper into Limitations and Delimitations (PhD student)
Organizing Your Social Sciences Research Paper: Limitations of the Study (USC Library)
Research Limitations (Research Methodology)
How to Present Limitations and Alternatives (UMASS)

Article References

Pearson-Stuttard, J., Kypridemos, C., Collins, B., Mozaffarian, D., Huang, Y., Bandosz, P.,…Micha, R. (2018). Estimating the health and economic effects of the proposed US Food and Drug Administration voluntary sodium reformulation: Microsimulation cost-effectiveness analysis. PLOS. https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002551

Xu, W.L, Pedersen, N.L., Keller, L., Kalpouzos, G., Wang, H.X., Graff, C,. Fratiglioni, L. (2015). HHEX_23 AA Genotype Exacerbates Effect of Diabetes on Dementia and Alzheimer Disease: A Population-Based Longitudinal Study. PLOS. Retrieved from https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001853

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Informed Consent
Writing Field Notes

The limitations of the study are those characteristics of design or methodology that impacted or influenced the application or interpretation of the results of your study. They are the constraints on generalizability and utility of findings that are the result of the ways in which you chose to design the study and/or the method used to establish internal and external validity.

Importance of...

Always acknowledge a study's limitations. It is far better for you to identify and acknowledge your study’s limitations than to have them pointed out by your professor and be graded down because you appear to have ignored them.

Keep in mind that acknowledgement of a study's limitations is an opportunity to make suggestions for further research . If you do connect your study's limitations to suggestions for further research, be sure to explain the ways in which these unanswered questions may become more focused because of your study.

Acknowledgement of a study's limitations also provides you with an opportunity to demonstrate to your professor that you have thought critically about the research problem, understood the relevant literature published about it, and correctly assessed the methods chosen for studying the problem. A key objective of the research process is not only discovering new knowledge but also to confront assumptions and explore what we don't know.

Claiming limitations is a subjective process because you must evaluate the impact of those limitations. Don't just list key weaknesses and the magnitude of a study's limitations. To do so diminishes the validity of your research because it leaves the reader wondering whether, or in what ways, limitation(s) in your study may have impacted the findings and conclusions. Limitations require a critical, overall appraisal and interpretation of their impact. You should answer the question: do these problems with errors, methods, validity, etc. eventually matter and, if so, to what extent?

Structure: How to Structure the Research Limitations Section of Your Dissertation . Dissertations and Theses: An Online Textbook. Laerd.com.

Descriptions of Possible Limitations

All studies have limitations. However, it is important that you restrict your discussion to limitations related to the research problem under investigation. For example, if a meta-analysis of existing literature is not a stated purpose of your research, it should not be discussed as a limitation. Do not apologize for not addressing issues that you did not promise to investigate in your paper.

Here are examples of limitations you may need to describe and to discuss how they possibly impacted your findings. Descriptions of limitations should be stated in the past tense.

Possible Methodological Limitations

Sample size -- the number of the units of analysis you use in your study is dictated by the type of research problem you are investigating. Note that, if your sample size is too small, it will be difficult to find significant relationships from the data, as statistical tests normally require a larger sample size to ensure a representative distribution of the population and to be considered representative of groups of people to whom results will be generalized or transferred.

Lack of available and/or reliable data -- a lack of data or of reliable data will likely require you to limit the scope of your analysis, the size of your sample, or it can be a significant obstacle in finding a trend and a meaningful relationship. You need to not only describe these limitations but to offer reasons why you believe data is missing or is unreliable. However, don’t just throw up your hands in frustration; use this as an opportunity to describe the need for future research.

Lack of prior research studies on the topic -- citing prior research studies forms the basis of your literature review and helps lay a foundation for understanding the research problem you are investigating. Depending on the currency or scope of your research topic, there may be little, if any, prior research on your topic. Before assuming this to be true, consult with a librarian! In cases when a librarian has confirmed that there is a lack of prior research, you may be required to develop an entirely new research typology [for example, using an exploratory rather than an explanatory research design]. Note that this limitation can serve as an important opportunity to describe the need for further research.

Measure used to collect the data -- sometimes it is the case that, after completing your interpretation of the findings, you discover that the way in which you gathered data inhibited your ability to conduct a thorough analysis of the results. For example, you regret not including a specific question in a survey that, in retrospect, could have helped address a particular issue that emerged later in the study. Acknowledge the deficiency by stating a need in future research to revise the specific method for gathering data.

Self-reported data -- whether you are relying on pre-existing self-reported data or you are conducting a qualitative research study and gathering the data yourself, self-reported data is limited by the fact that it rarely can be independently verified. In other words, you must take what people say, whether in interviews, focus groups, or on questionnaires, at face value. However, self-reported data contain several potential sources of bias that should be noted as limitations: (1) selective memory (remembering or not remembering experiences or events that occurred at some point in the past); (2) telescoping [recalling events that occurred at one time as if they occurred at another time]; (3) attribution [the act of attributing positive events and outcomes to one's own agency but attributing negative events and outcomes to external forces]; and, (4) exaggeration [the act of representing outcomes or embellishing events as more significant than is actually suggested from other data].

Possible Limitations of the Researcher

Access -- if your study depends on having access to people, organizations, or documents and, for whatever reason, access is denied or otherwise limited, the reasons for this need to be described.

Longitudinal effects -- unlike your professor, who can devote years [even a lifetime] to studying a single research problem, the time available to investigate a research problem and to measure change or stability within a sample is constrained by the due date of your assignment. Be sure to choose a topic that does not require an excessive amount of time to complete the literature review, apply the methodology, and gather and interpret the results. If you're unsure, talk to your professor.

Cultural and other types of bias -- we all have biases, whether we are conscience of them or not. Bias is when a person, place, or thing is viewed or shown in a consistently inaccurate way. It is usually negative, though one can have a positive bias as well. When proof-reading your paper, be especially critical in reviewing how you have stated a problem, selected the data to be studied, what may have been omitted, the way you have ordered events, people, or places and how you have chosen to represent a person, place, or thing, to name a phenomenon, or to use possible words with a positive or negative connotation. Note that if you detect bias in prior research, it must be acknowledged, and you should explain what measures were taken to avoid perpetuating bias.

Fluency in a language -- if your research focuses on measuring the perceived value of after-school tutoring among Mexican American ESL [English as a Second Language] students, for example, and you are not fluent in Spanish, you are limited in being able to read and interpret Spanish language research studies on the topic. This deficiency should be acknowledged.

Structure and Writing Style

Information about the limitations of your study is generally placed either at the beginning of the discussion section of your paper so the reader knows and understands the limitations before reading the rest of your analysis of the findings, or the limitations are outlined at the conclusion of the discussion section as an acknowledgement of the need for further study. Statements about a study's limitations should not be buried in the body [middle] of the discussion section unless a limitation is specific to something covered in that part of the paper. If this is the case, though, the limitation should be reiterated at the conclusion of the section.

If you determine that your study is seriously flawed due to important limitations, such as an inability to acquire critical data, consider reframing it as a pilot study intended to lay the groundwork for a more complete research study in the future. Be sure, though, to specifically explain the ways that these flaws can be successfully overcome in later studies.

But do not use this as an excuse for not developing a thorough research paper! Review the tab in this guide for developing a research topic. If serious limitations exist, it generally indicates a likelihood that your research problem is too narrowly defined or that the issue or event under study is too recent and, thus, very little research has been written about it. If serious limitations do emerge, consult with your professor about possible ways to overcome them or how to reframe your study.

When discussing the limitations of your research, be sure to:

Describe each limitation in detailed but concise terms;

Explain why each limitation exists;

Provide the reasons why each limitation could not be overcome using the method(s) chosen to gather the data [cite to other studies that had similar problems when possible];

Assess the impact of each limitation in relation to the overall findings and conclusions of your study; and,

If appropriate, describe how these limitations could point to the need for further research.

Remember that the method you chose may be the source of a significant limitation that has emerged during your interpretation of the results [for example, you didn't ask a particular question in a survey that you later wish you had]. If this is the case, don't panic. Acknowledge it and explain how applying a different or more robust methodology might address the research problem more effectively in any future study. An underlying goal of scholarly research is not only to prove what works, but to demonstrate what doesn't work or what needs further clarification.

Brutus, Stéphane et al. Self-Reported Limitations and Future Directions in Scholarly Reports: Analysis and Recommendations. Journal of Management 39 (January 2013): 48-75; Ioannidis, John P.A. Limitations are not Properly Acknowledged in the Scientific Literature. Journal of Clinical Epidemiology 60 (2007): 324-329; Pasek, Josh. Writing the Empirical Social Science Research Paper: A Guide for the Perplexed . January 24, 2012. Academia.edu; Structure: How to Structure the Research Limitations Section of Your Dissertation . Dissertations and Theses: An Online Textbook. Laerd.com; What Is an Academic Paper? Institute for Writing Rhetoric. Dartmouth College; Writing the Experimental Report: Methods, Results, and Discussion. The Writing Lab and The OWL. Purdue University.

Writing Tip

Don't Inflate the Importance of Your Findings! After all the hard work and long hours devoted to writing your research paper, it is easy to get carried away with attributing unwarranted importance to what you’ve done. We all want our academic work to be viewed as excellent and worthy of a good grade, but it is important that you understand and openly acknowledge the limitations of your study. Inflating the importance of your study's findings in an attempt to hide its flaws is a big turn off to your readers. A measure of humility goes a long way!

Another Writing Tip

Negative Results are Not a Limitation!

Negative evidence refers to findings that unexpectedly challenge rather than support your hypothesis. If you didn't get the results you anticipated, it may mean your hypothesis was incorrect and needs to be reformulated, or perhaps you have stumbled onto something unexpected that warrants further study. Moreover, the absence of an effect may be very telling in many situations, particularly in experimental research designs. In any case, your results may be of importance to others even though they did not support your hypothesis. Do not fall into the trap of thinking that results contrary to what you expected is a limitation to your study. If you carried out the research well, they are simply your results and only require additional interpretation.

Yet Another Writing Tip

A Note about Sample Size Limitations in Qualitative Research

Sample sizes are typically smaller in qualitative research because, as the study goes on, acquiring more data does not necessarily lead to more information. This is because one occurrence of a piece of data, or a code, is all that is necessary to ensure that it becomes part of the analysis framework. However, it remains true that sample sizes that are too small cannot adequately support claims of having achieved valid conclusions and sample sizes that are too large do not permit the deep, naturalistic, and inductive analysis that defines qualitative inquiry. Determining adequate sample size in qualitative research is ultimately a matter of judgment and experience in evaluating the quality of the information collected against the uses to which it will be applied, and the particular research method and purposeful sampling strategy employed. If the sample size is found to be a limitation, it may reflect your judgement about the methodological technique chosen [e.g., single life history study versus focus group interviews] rather than the number of respondents used.

Huberman, A. Michael and Matthew B. Miles. Data Management and Analysis Methods. In Handbook of Qualitative Research. Norman K. Denzin and Yvonna S. Lincoln, eds. (Thousand Oaks, CA: Sage, 1994), pp. 428-444.

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Writing Tips

How to Identify Limitations in Research

4-minute read

7th March 2022

Whether you’re a veteran researcher with years of experience under your belt or a novice to the field that’s feeling overwhelmed with where to start, you must understand that every study has its limitations. These are restrictions that arise from the study’s design, or the methodology implemented during the testing phase. Unfortunately, research limitations will always exist due to the subjective nature of testing a hypothesis. We’ve compiled some helpful information below on how to identify and accept research limitations and use them to your advantage. Essentially, we’ll show you how to make lemonade (a brilliant piece of academic work ) from the lemons you receive (the constraints your study reveals).

Research Limitations

So, let’s dive straight in, shall we? It’s always beneficial (and good practice) to disclose your research limitations . A common thought is that divulging these shortcomings will undermine the credibility and quality of your research. However, this is certainly not the case— stating the facts upfront not only reinforces your reputation as a researcher but also lets the assessor or reader know that you’re confident and transparent about the results and relevance of your study, despite these constraints.

Additionally, it creates a gap for more research opportunities, where you can analyze these limitations and determine how to incorporate or address them in a new batch of tests or create a new hypothesis altogether. Another bonus is that it helps readers to understand the optimum conditions for how to apply the results of your testing. This is a win-win, making for a far more persuasive research paper .

Now that you know why you should clarify your research limitations, let’s focus on which ones take precedence and should be disclosed. Any given research project can be vulnerable to various hindrances, so how do you identify them and single out the most significant ones to discuss? Well, that depends entirely on the nature of your study. You’ll need to comb through your research approach, methodology, testing processes, and expected results to identify the type of limitations your study may be exposed to. It’s worth noting that this understanding can only offer a broad idea of the possible restrictions you’ll face and may potentially change throughout the study.

We’ve compiled a list of the most common types of research limitations that you may encounter so you can adequately prepare for them and remain vigilant during each stage of your study.

Sample Size:

It’s critical that you choose a sample size that accurately represents the population you wish to test your theory on. If a sample is too small, the results cannot reliably be generalized across a large population.

Methodology:

The method you choose before you commence testing might seem effective in theory, but too many stumbling blocks during the testing phase can influence the accuracy and reliability of the results.

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Collection of Data:

The methods you utilize to obtain your research—surveys, emails, in-person interviews, phone calls—will directly influence the type of results your study yields.

Age of Data:

The nature of the information—and how far back it goes—affects the type of assumptions you can make. Extrapolating older data for a current hypothesis can significantly change the outcome of your testing.

Time Constraints:

Working within the deadline of when you need to submit your findings will determine the extent of your research and testing and, therefore, can heavily impact your results. Limited time frames for testing might mean not achieving the scope of results you were originally looking for.

Limited Budget:

Your study may require equipment and other resources that can become extremely costly. Budget constraints may mean you cannot acquire advanced software, programs, or travel to multiple destinations to interview participants. All of these factors can substantially influence your results.

So, now that you know how to determine your research limitations and the types you might experience, where should you document it? It’s commonly disclosed at the beginning of your discussion section , so the reader understands the shortcomings of your study before digging into the juicy bit—your findings. Alternatively, you can detail the constraints faced at the end of the discussion section to emphasize the requirements for the completion of further studies.

We hope this post will prepare you for some of the pitfalls you may encounter when conducting and documenting your research. Once you have a first draft ready, consider submitting a free sample to us for proofreading to ensure that your writing is concise and error-free and your results—despite their limitations— shine through.

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Scientists seek to invent a safe, reliable, and cheap battery for electricity grids

The new Aqueous Battery Consortium of Stanford, SLAC, and 13 other research institutions, funded by the U.S. Department of Energy, seeks to overcome the limitations of a battery using water as its electrolyte.

How do you store electricity in a way that is large and powerful enough to support the electric grid, as well as reliable, safe, environmentally sustainable, and inexpensive? One way may be to make a major component of the rechargeable battery mostly from water and the rest of the device primarily from abundant materials.

That is the vision of dozens of the best energy storage experts from 15 research institutions across the United States and Canada, led by Stanford University and SLAC National Accelerator Laboratory . After a competitive process, the U.S. Department of Energy announced on Sept. 3 its support for this energy hub research project, called the Aqueous Battery Consortium. The project can receive up to $62.5 million over five years as part of the DOE’s Energy Innovation Hubs program. The other battery-centered Energy Innovation Hub announced today by the DOE is the Energy Storage Research Alliance, led by Argonne National Laboratory.

“This project will undertake the grand challenge of electrochemical energy storage in a world dependent on intermittent solar and wind power. We need affordable, grid-scale energy storage that will work dependably for a long time,” said the project’s director, Yi Cui , a Stanford professor of materials science and engineering, of energy science and engineering, and of photon science at SLAC.

A huge amount of stationary energy storage will be needed to reduce net global greenhouse gas emissions to zero, said Cui, and water is the only realistic solvent available at the quantity and cost needed for such batteries.

“How do we control charge transfer between solids and water from the molecular to the device scale and achieve reversibility with an efficiency of nearly 100 percent?” asked Cui. “We don’t know the solutions to those hard problems, but with the Department of Energy's support we intend to find out.”

A new aqueous battery

The lead-acid batteries that start combustion engines in conventional vehicles are a type of aqueous battery that has been in wide use for decades. However, for their size, lead-acid car batteries do not hold much energy, even though they can briefly supply a surge of current to start your car.

Also, the lead in them is toxic. Of all lead produced globally, 85 percent goes into lead-acid batteries. Although new batteries mostly use lead from recycled ones, in many countries the recycling process relies on techniques that pollute the environment and hurt human health. One in three children suffer from lead poisoning globally, according to a 2020 UNICEF report , with much of the suffering in developing economies.

With such catastrophes in mind, the research team prioritizes environmental justice, as well as the vision of sustainable, affordable, and secure energy for all people. “We hope our inventions may someday benefit all of humanity,” said Cui.

The new research project aims to develop a new kind of aqueous battery, one that is environmentally safe, has higher energy density than lead-acid batteries, and costs one-tenth that of lithium-ion batteries today. The group plans to keep costs for this future technology low by using cheaper raw materials, simpler electronics, and new, efficient manufacturing techniques. The pursued technology is also expected to be safer, and to create batteries that charge and discharge quickly.

However, “the barriers to such a new aqueous battery have stymied inventors for years,” said the project’s chief scientist, Linda Nazar , a professor of chemistry at the University of Waterloo in Ontario, Canada. Nazar has developed new materials for energy storage and conversion for the past 20 years, including aqueous batteries. “In addition to stubbornly low voltage and energy density, water can corrode battery materials, become the source of undesirable side reactions, and the cells can fail after just hundreds of charge-discharge cycles under demanding practical conditions.”

The Aqueous Battery Consortium, which will be administered by Stanford’s Precourt Institute for Energy , hopes to overcome all these challenges and, in so doing, advance battery technology broadly. The team consists of 31 leading battery scientists, engineers, and physicists from 12 universities in North America, as well as from SLAC, the U.S. Army Research Lab , and the U.S. Naval Research Lab .

Project organization

The 31 co-principal investigators and the much larger number of students and postdoctoral scholars working with the investigators are organized into six teams working on broad research aims and three teams working on challenges that cut across those goals. The research Aims cover the electrolyte, both electrodes, electrolyte/electrode interface, corrosion, and overall device architecture. The three Crosscutting Theme teams will work on materials design and synthesis, coordinated theory and simulation, and characterization of prototype devices in operation.

To ensure collaboration and interdisciplinary thinking across the project, each researcher is on at least one of the six Aims teams and at least one of the Crosscutting Theme teams.

“Our ambitious goals can be met only by a well-integrated team of experts working across disciplines, who encourage each other to think from fresh angles and with novel viewpoints,” said Johanna Nelson Weker , the Aqueous Battery Consortium’s assistant director and lead scientist in SLAC's Stanford Synchrotron Radiation Lightsource division.

“One of the teams I’m on includes a couple of physicists, a professor of chemistry, and a professor of mechanical engineering, among other disciplines,” said Nelson Weker, “but all the researchers in the project have done much work on energy storage.”

Regular meetings of all consortium members and participation in various scientific forums should help create a large intellectual community of energy storage researchers. The consortium’s leaders hope this community will include not just the co-principal investigators, but also the scores of graduate students and postdoctoral scholars who will perform much of the research, and other battery scientists around the world. The researchers hope the Aqueous Battery Consortium will become a dynamic center for all aqueous battery research – not just its research – domestically and worldwide.

Management and oversight

The Aqueous Battery Consortium’s chief operations officer is Steve Eglash , director of the Applied Energy Division and interim chief research officer at SLAC. He is responsible for the organizational and administrative leadership of the project, including financial and personnel management, tracking and reporting research progress to the Department of Energy, environmental health and safety, and relationships with external partners.

“The Aqueous Battery Consortium is dedicated to doing the scientific research that will enable large-scale deployment of aqueous batteries," said Eglash. "The consortium will be accountable to a governance board and get external advice from two advisory boards. One will advise us on the scientific direction of our work. The other will advise us on the relevance of our work to commercial applications."

The project’s governance board will ensure institutional support and compliance. It will be led by Arun Majumdar , dean of the Stanford Doerr School of Sustainability , and professor of mechanical engineering, energy science and engineering, and photon science. Steven Chu , Nobel physicist and former U.S. Secretary of Energy, will helm the scientific advisory board. Chu, Stanford professor of physics, physiology, and energy science and engineering, is also one of the project’s researchers. Ira Ehrenpreis , co-founder and managing partner of the investment fund DBL Partners, will chair the technology review board. Ehrenpreis also co-chairs the Precourt Institute for Energy's advisory council.

“Also, to make sure we are doing things correctly and consistently across the project, several team members have taken on the responsibility for overseeing crucial practices. These include data management, technology transfer, environmental health and safety, and diversity, equity and inclusion,” said Eglash, who noted that five of the consortium's 12 universities are designated minority-serving institutions.

In addition to Stanford and the University of Waterloo, the other universities contributing investigators to this project are California State University, Long Beach ; Florida A&M University/Florida State University's College of Engineering ; North Carolina State University ; Oregon State University ; San Jose State University ; UCLA ; UC-San Diego ; UC-Santa Barbara ; University of Maryland ; and University of Texas at Austin .

The co-principal investigators page on this website lists all senior researchers with links to their personal profile pages.

Cui is also the director of the Sustainability Accelerator at the Stanford Doerr School of Sustainability, the immediate past director of the Precourt Institute for Energy, current co-director of the institute’s StorageX Initiative and director of its postdoctoral program , as well as founder of a publicly traded battery company. Nazar is also a fellow of the Royal Society (Canada) and of the Royal Society (U.K.), as well as a Tier 1 Canada Research Chair in Solid State Energy Materials. Majumdar is also a senior fellow at the Precourt Institute and at the Hoover Institution. Ehrenpreis, an alumnus of Stanford’s Graduate School of Business and Stanford Law School, is also on Tesla Motor’s board of directors. The Precourt Institute is part of the Stanford Doerr School of Sustainability.

Media contact: Mark Golden , Communications Director, Precourt Institute for Energy and Aqueous Battery Consortium

Explore More

Department of Energy Awards $125 Million for Research to Enable Next-Generation Batteries and Energy Storage

The two Energy Innovation Hub teams, led by Stanford and Argonne National Laboratory, will emphasize multi-disciplinary fundamental research to address long-standing and emerging challenges for rechargeable batteries.

Open access
Published: 02 September 2024

Collecting and reporting adverse events in low-income settings—perspectives from vaccine trials in the Gambia

Andrew Ayi-Ashong Bruce ORCID: orcid.org/0009-0006-8597-5975 1 ,
Ama-Onyebuchi Umesi 1 ,
Adedapo Bashorun 1 ,
Magnus Ochoge 1 ,
Mohammed Yisa 1 ,
Dolapo Obayemi-Ajiboye 1 ,
Ahmed Futa 1 ,
Anna Njie 1 ,
Selasi Asase 1 ,
Modou Bella Jallow 1 ,
Larry Kotei 1 ,
Lucy Affleck 1 ,
Olubunmi Abiola Olubiyi 1 ,
Lamin B. Jarju 1 ,
Madi Kanyi 1 ,
Baba Danso 1 ,
Armel Zemsi 1 &
Ed Clarke 1

Trials volume 25 , Article number: 579 ( 2024 ) Cite this article

Metrics details

Despite Africa’s significant infectious disease burden, it is underrepresented in global vaccine clinical trials. While this trend is slowly reversing, it is important to recognize and mitigate the challenges that arise when conducting vaccine clinical trials in this environment. These challenges stem from a variety of factors peculiar to the population and may negatively impact adverse event collection and reporting if not properly addressed.

As a team of clinical researchers working within the MRCG (Medical Research Council Unit The Gambia), we have conducted 12 phase 1 to 3 vaccine trials over the past 10 years. In this article, we discuss the challenges we face and the strategies we have developed to improve the collection and reporting of adverse events in low-income settings.

Healthcare-seeking behaviors in the Gambia are influenced by spiritual and cultural beliefs as well as barriers to accessing orthodox healthcare; participants in trials may resort to non-orthodox care, reducing the accuracy of reported adverse events. To address this, trial eligibility criteria prohibit self-treatment and herbal product use during trials. Instead, round-the-clock care is provided to trial participants, facilitating safety follow-up.

Constraints in the healthcare system in the Gambia such as limitations in diagnostic tools limit the specificity of diagnosis when reporting adverse events. To overcome these challenges, the Medical Research Council Unit maintains a Clinical Services Department, offering medical care and diagnostic services to study participants.

Sociocultural factors, including low literacy rates and social influences, impact adverse event collection. Solicited adverse events are collected during home visits on paper-based or electronic report forms.

Community engagement meetings are held before each study starts to inform community stakeholders about the study and answer any questions they may have. These meetings ensure that influential members of the community understand the purpose of the study and the risks and benefits of participating in the trial. This understanding makes them more likely to support participation within their communities.

Conducting ethical vaccine clinical trials in resource-limited settings requires strategies to accurately collect and report adverse events. Our experiences from the Gambia offer insights into adverse event collection in these settings.

Peer Review reports

Introduction

Clinical trials play a crucial role in assessing the efficacy and safety of medicines, vaccines, and other treatment methods before licensure and in subsequently optimizing their use in new populations and according to new dosing schedules [ 1 ]. However, while Africa comprises 17% of the world’s population and carries around 25% of the global disease burden [ 2 , 3 ], this is not reflected in the number of clinical trials undertaken on the continent [ 4 , 5 ]. Conducting clinical trials in Africa is vital for developing vaccines and treatments for diseases that primarily burden the region [ 6 ]. First, significant progress has been made in the development of vaccines for malaria and Ebola virus disease only through clinical trials conducted here [ 7 , 8 ]. The high incidence of malaria, with over 90% of cases occurring in the region [ 9 ], makes it possible to assess efficacy while keeping in line with the ethical principles of equity and justice. Second, extrapolating data from other settings and populations to guide policy in Africa may be unsafe due to distinct socioeconomic, genetic, and environmental differences between regions [ 6 , 10 , 11 ]. For example, while the efficacy of the oral rotavirus vaccines in trials conducted in high-income countries was over 90% over the first 2 years of life, in low-income settings in Africa and elsewhere, the efficacy was considerably lower at below 35% over the first 2 years of life [ 12 ]. Finally, as demonstrated during COVID-19, the continent cannot rely on the equitable distribution of vaccines, even in the context of a global pandemic [ 13 ]. The Partnership for African Vaccine Manufacturing (PAVM), led by the African Union and Africa Centres for Disease Control and Prevention, is addressing this and aims for 60% of vaccines to be manufactured locally on the continent by 2040 [ 14 ]. Conducting clinical trials in Africa will contribute to this vision by building local expertise and capacity as well as establishing regulatory frameworks and quality standards essential for vaccine manufacturing.

International ethical standards, including the Declaration of Helsinki and the International Council on Harmonization Guidelines for Good Clinical Practice (ICH-GCP), have been established to harmonize the conduct of clinical trials across settings and ensure the safety of participants [ 15 , 16 ]. According to the ICH-GCP (ICH GCP, E6(R2) 1.2), an adverse event (AE) is defined as “any untoward medical occurrence in a participant administered a study product, which does not necessarily have a causal relationship with the study product itself.” An adverse event is defined as serious (i.e., an SAE) if it results in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, and results in persistent or significant disability/incapacity or a congenital anomaly/birth defect [ 17 ]. Good clinical practice guidelines require that all serious adverse events be reported to the relevant sponsor and institutional review board; hence, the identification and reporting of adverse events are important components of ensuring safety in vaccine clinical trials [ 18 ]. Furthermore, vaccines are generally held to a higher safety standard than other medications as they are generally administered to healthy individuals for disease prevention rather than treatment [ 19 ]. Consequently, accurately collecting and reporting adverse events comprehensively in vaccine clinical trials is vital to ensuring public trust in the vaccine development process [ 20 , 21 ].

The Gambia has a population of 2.4 million people, with a gross domestic product per capita of $808 [ 22 ]. Although progress has been made in recent years [ 23 ], the under-5 mortality rate, of 47.9 deaths per 1000 live births, is significantly above the average of 5 deaths per 1000 live births in high-income countries [ 24 , 25 ]. Lower respiratory tract infections and diarrheal diseases are major contributors to child morbidity and mortality [ 26 , 27 , 28 ]. The physician and nurse density in the Gambia is 1.4 doctors and 19.4 nurses and midwives per 10,000 population respectively, compared to an average of 33.4 doctors and 114.9 nurses and midwives in high-income countries [ 29 ].

English is the official national language of the Gambia; however, adult literacy rates are relatively low, at 51.2% for women and 65.2% for men [ 30 ]. A wide range of languages are spoken, but they are not commonly used in written form. These include Mandinka (38%), Wolof (18%), and Fula (21%) [ 31 , 32 ]. Thirty-three per cent of the population have access to the Internet [ 33 ]. Overall, 95% of the Gambian population is Muslim, with Christianity and West African traditional religions making up the remainder [ 31 ].

The Medical Research Council Unit The Gambia (MRCG) is a research institution that has been conducting medical research in the Gambia and elsewhere in West Africa for over 75 years. The first trials as well as key efficacy trials of Haemophilus influenzae type b (Hib) and pneumococcal-conjugate vaccines and the first trials of the RTS/S malaria vaccine in Africa were conducted at the Unit [ 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. As a team of researchers working within the MRCG, we have conducted 12 phase 1 to 3 vaccine trials over the past 10 years. These trials have ranged in size from less than 100 to more than 3000 participants, enrolling newborns, infants, children, and adults as well as a series of trials enrolling pregnant women, achieving retention rates ranging from 603/660 [91.4%] to 345/346 [99.7%]. Consequently, we have gained considerable experience collecting and reporting adverse events in this setting.

In this article, we explore the context-specific issues and the strategies we have developed to ensure we collect robust safety data in our context.

Health-seeking behavior

Healthcare-seeking behaviors are defined as actions an individual undertakes to find a remedy when they have a health problem [ 41 ]. These behaviors are influenced by religious and cultural beliefs as well as the availability, accessibility, and affordability of healthcare [ 42 , 43 ]. Health-seeking behaviors are particularly important in vaccine trials because participants are typically healthy and may dismiss mild symptoms as unrelated to the study product. A study conducted in the Gambia revealed that only half of parents of children under 5 with a febrile illness sought initial care at a health facility, with 12% first visiting a pharmacy and 5% consulting a traditional healer. Forty-nine percent of individuals chose to seek care from alternative health providers due to their greater accessibility within the local community [ 42 ].

Self-medication

When participants or their parents (in pediatric populations) opt for self-treatment, we find that they may not disclose clinical events they experience to clinical trial staff. Furthermore, side effects of these unreported concomitant medications may be incorrectly reported as adverse events due to the investigational product. This is especially important as the country has historically lacked the necessary laboratory facilities for quality control checks on imported drugs, leading to instances of unsafe medications being available over the counter. For instance, between June to September 2022, 66 children died due to contaminated cough syrup containing diethylene glycol and ethylene glycol sold over the counter [ 44 ]. This was traced to an Indian pharmaceutical manufacturer and has resulted in a significant tightening in the application of import regulations.

Traditional/spiritual healers

It has been estimated that over 80% of the population of sub-Saharan Africa uses traditional medicines, either independently or as an adjunct to orthodox medicine [ 45 ]. Many Gambians believe illness has either a biomedical basis (referred to as kuraŋ keso in Mandinka) or is a result of supernatural causes ( ming kesa sande in Mandinka), such as djinn spirits and witchcraft [ 46 ]. For example, seizures are often believed to be of spiritual origin. These strongly held beliefs about the spiritual origin of disease can be resistant to change. Participants seeking the services of a traditional healer may forget to report adverse events once symptoms resolve or may choose to conceal them, perceiving them to be outside the realm of biomedicine.

Additionally, some herbal medications have been reported to be toxic to the liver or kidneys [ 47 , 48 ]. For example, a study conducted in Nigeria found that over one-third of cases of acute tubular necrosis were due to the use of traditional herbal medicines [ 49 ]. It is frequently challenging to clearly define the impact of the concurrent use of traditional medicines and their associated side effects in the reporting and assessment of adverse events in clinical trials. Moreover, in most cases, there is limited information about the nature of the medications taken, which are not labeled or regulated in the same way, making it difficult to establish definitively what was consumed.

To limit the impact of self-medication, a requirement for participants to abstain from self-treatment and the use of herbal products during the trial is typically included within the eligibility criteria for the trial [ 50 , 51 , 52 ]. This is reaffirmed at each study visit. Furthermore, study sites maintain an on-call rota of clinicians, nurses, field workers, and drivers to respond to any concerns out-of-hours, thus minimizing the need to seek alternative forms of care. Participants are provided with mobile phones that enable free phone calls to the trial staff. This enables participants to contact the study team at any time and allows the study team to reach out for safety follow-up. When a participant calls the team to report a medical concern, different approaches are taken depending on the nature of the complaint; the participant may be reassured, visited at home, or transported to the MRCG clinic for an in-person consultation, where free treatment is provided according to accepted medical standards in the Gambia. In cases where participants are visited at home, all decisions about health concerns are made together with a study doctor. This ensures that all adverse events and concomitant medications are captured and recorded.

When encouraging participants to avoid traditional medicines, it is crucial to approach this non-judgmentally, to avoid under-reporting related to social desirability and the perceived biomedical focus of the study team. Participants are encouraged to disclose any herbal products used and reminded to contact study staff for all clinical concerns. One study indicated that over 50% of users of traditional medicine failed to disclose their use to their healthcare providers [ 53 ].

Health systems

The Gambia, like many sub-Saharan African countries, has a healthcare system with finite human resources, physical infrastructure, and diagnostic and clinical supply capacity. The collection and reporting of adverse events must be considered with such limitations in mind.

Healthcare provision

Providing free healthcare to participants in the context of a constrained healthcare system can paradoxically result in overreporting adverse events due to participants reporting illnesses to obtain free medication for other family members. In addition, the provision of free medical care may be perceived as an undue influence on a participant’s decision to join a trial and risks some parents allowing their child to join a study solely for access to medication, rather than making an informed decision based on understanding the purpose, risks and benefits of the trial.

Diagnostic limitations

With limited support from routine laboratory and radiological services, clinicians depend more heavily on clinical skills alone to make diagnoses. This limitation typically reduces the specificity of diagnoses. Moreover, cultural beliefs and the short time to burial following death in the Islamic religion, as well as limited capacity for postmortem examination, reduce the ability to determine the cause of death, even in trial participants.

Lack of reliable background data

The absence of robust epidemiological and surveillance data may hinder the analysis of vaccine safety signals. During active follow-up on adverse events in trials, there may be an increase in reported safety events due to the nature of follow-up, compared to data based on passive reporting which may or may not be available. This risks generating apparent safety signals in trials and raising safety concerns that may not be warranted.

Accurate collection of adverse events offers indirect benefits to the parents, providing an opportunity for health education on optimal feeding practices and other relevant healthcare-related topics. In addition, MRCG has an established Clinical Services Department (CSD) that provides outpatient and inpatient medical care to study participants as well as the local population. The department also runs ISO15189 and Good Clinical Laboratory Practice (GCLP) accredited laboratory services and radiology services. Furthermore, studies may establish trial-specific additional capacity to characterize adverse events of special interest more fully, such as using respiratory virus multiplex panels and bacterial culture and serotyping. In cases where participants die outside a healthcare facility, verbal autopsies are conducted. These involve standardized interviews with the deceased person’s next of kin to determine the cause of death. One study found 67% to 80% concordance between the diagnosis from verbal autopsy and the diagnosis on the death certificate [ 54 ]. The use of the minimally invasive autopsy procedures currently under development in related context may further improve this in the future [ 55 ].

To limit the overreporting of illnesses during clinical trials, clinical guidelines are used to ensure only medications routinely used in the Gambian healthcare system are prescribed and that thorough clinical assessments are undertaken ensuring the provision of medications to trial participants alone based on clinical indication. The MRCG has also conducted a wide variety of epidemiological studies to enhance the understanding of background disease rates including within three established Health and Demographic Surveillance Systems.

Sociocultural considerations

Literacy rates.

In many clinical trials conducted in high-income settings with high literacy rates and internet penetration, participants are provided with diary cards or smartphone apps to document solicited adverse events in the days following the administration of the study product [ 56 , 57 ]. While this approach facilitates the systematic and real-time collection of adverse events, replicating it in settings in which literacy is limited and internet access inconsistent is challenging. Participants may struggle to reliably self-report adverse events on a diary card or smartphone app.

Highly mobile population

Due to historical factors and shared linguistic and cultural features, tribes and families span international borders, leading to significant internal and international migration between the Gambia, Senegal, Guinea-Bissau, and Guinea-Conakry [ 58 ]. Participants frequently travel across international borders, presenting challenges in collecting adverse events, particularly when they do so without informing the study team in advance. Rarely, this leads to participants being lost to follow-up, resulting in incomplete data and unreported adverse events.

Social dynamics

Social influence significantly affects individuals’ decisions to participate in trials and report adverse events to study staff [ 42 , 59 ]. Healthy participants in vaccine trials may have lower incentives to participate in the trial and report adverse events accurately. Additionally, friends and family may influence study participants to seek care from alternative healthcare providers, leading to potential underreporting of adverse events. In the Gambia, a patriarchal society, women often require approval from husbands, fathers, or other significant male figures before seeking medical care for themselves or their children. This contributes to delayed reporting of adverse events when women are compelled to wait for approval from their fathers or husbands before contacting the study team.

The MRCG has developed significant visibility in the communities in which clinical studies are conducted. In our studies, we do not offer financial incentives to participants, yet we achieve high participation rates through robust community engagement and support. The Unit is well regarded due to the positive impact of research on the communities involved. However, rumors, particularly regarding MRCG “selling” blood samples, persist, which may make people reluctant to enroll in studies and participants less likely to accept blood sampling as part of safety follow-up.

Field staff are crucial members of the team who help to mitigate the challenges mentioned above. To replace diary cards given to participants, field staff conduct home visits to collect adverse events. They are provided with paper or electronic case report forms on tablets with online and offline functionality which they use during daily visits to participants’ homes following vaccination. We rely on participants providing detailed directions to their homes, due to the lack of street names and house numbers in many parts of the Gambia. In addition, to ensure data quality and consistency, a percentage of these home visits undergo spot checks by senior field staff with data subsequently being reviewed by a trial clinician.

To mitigate the challenge of participants moving out of the study area, we ensure that potential participants have no imminent travel plans for the duration of the study. Field staff are assigned to individual participants to maintain regular contact throughout the study period, increasing the likelihood that we are aware if participants plan to relocate. When a participant travels out of the study area, contact is maintained via telephone and a field worker is dispatched to their location to collect adverse events. Given the small size of the Gambia, we regularly follow participants across the country.

To ensure community engagement and support during clinical trials, community sensitization meetings are held at the beginning of every trial, with community advisory boards (CAB) increasingly playing a role in the design and set up of the studies being conducted. Community sensitization meetings inform the community about the upcoming trial, address questions and rumors, and obtain permission from the village chief (Alkalo) and other key stakeholders to conduct research in the community. At the end of a clinical trial, open days are held to feedback the results of the trial to the community. Community meetings, CABs, and open days are in line with Good Participatory Practice [ 60 ] and ensure that not only potential participants but also other influential members of the community understand why the trial is being conducted as well as its procedures, risks, and benefits. This understanding makes them likely to accommodate and support participation within communities. Most members of the field team are resident in the local communities and are therefore able to detect rumors early and arrange additional community sensitization meetings to address these rumors. Our community engagement activities have led to routinely high recruitment and retention rates. The key challenges we have encountered and strategies we have implemented to address them are summarized in Table 1 .

The challenges we face in collecting adverse events are not unique to the Gambia, as similar conditions are prevalent in other low-income countries. These countries often have similar health-seeking behaviors and social dynamics, weak health systems, and populations with low literacy rates. Therefore, we expect that the strategies we have developed will be generally applicable in other low-income contexts.

Implementing some strategies can be relatively straightforward, such as organizing community sensitization meetings and open days to improve community engagement. Requiring participants to abstain from self-medication and herbal products during the study also helps improve adverse event collection; however, studies that implement such requirements will benefit from committing to providing healthcare for participants throughout the study. This can be achieved by partnering with clinics and hospitals to ensure that participants receive standardized care throughout the study. Conducting home visits to collect adverse events can also be implemented in clinical trials. This active method of collecting adverse events improves the accuracy of reported adverse events.

Other strategies, such as conducting epidemiological studies and establishing health demographic surveys, may be more difficult to implement. These are made possible by the resources available at established research institutions like the MRCG. We recommend increased collaboration between researchers and institutions to allow for the pooling of resources. This will also allow researchers to benefit from the resources available in large institutions across the continent.

This commentary represents the experiences of a diverse team of researchers who have worked together over time. However, we recognize that valuable additional strategies may have been excluded. While many of the points raised apply beyond the Gambia, we also recognize some strategies are context-specific, and local knowledge is essential in their application in other low-income countries.

Conducting clinical research according to international ethical standards in resource-limited settings is vital but poses challenges. We have developed strategies to ensure adverse event data are robust in vaccine trials conducted in the Gambia. While context specific, these insights may be of value to researchers undertaking vaccine and other clinical trials in related settings.

Availability of data and materials

Not applicable.

Abbreviations

Adverse event

Africa Centres for Disease Control and Prevention

Clinical Services Department

Good Clinical Laboratory Practice

International Council on Harmonization Guidelines for Good Clinical Practice

Medical Research Council Unit The Gambia

Partnership for African Vaccine Manufacturing

Serious adverse event

Hansson SO. Why and for what are clinical trials the gold standard? Scandinavian Journal of Public Health. 2014;42(13_suppl):41–8.

Niohuru I. Disease Burden and Mortality. In: Niohuru I, editor. Healthcare and disease burden in Africa: the impact of socioeconomic factors on public health. Cham: Springer International Publishing; 2023. p. 35–85.

Chapter Google Scholar

Worldometer. Africa population [11 Jan 2024]. Available from: https://www.worldometers.info/world-population/africa-population/#:~:text=Africa%20Population%20(LIVE)&text=Africa%20population%20is%20equivalent%20to,%22)%2C%20ordered%20by%20population .

Viergever RF, Li K. Trends in global clinical trial registration: an analysis of numbers of registered clinical trials in different parts of the world from 2004 to 2013. BMJ Open. 2015;5(9): e008932.

Article PubMed PubMed Central Google Scholar

Taylor-Robinson SD, Spearman CW, Suliman AAA. Why is there a paucity of clinical trials in Africa? QJM. 2021;114(6):357–8.

Article CAS PubMed Google Scholar

Marincola E, Kariuki T. Quality research in Africa and why it is important. ACS Omega. 2020;5(38):24155–7.

Article CAS PubMed PubMed Central Google Scholar

Agnandji ST, Lell B, Soulanoudjingar SS, Fernandes JF, Abossolo BP, Conzelmann C, et al. First results of phase 3 trial of RTS, S/AS01 malaria vaccine in African children. N Engl J Med. 2011;365(20):1863–75.

Article PubMed Google Scholar

Sulis G, Peebles A, Basta NE. Lassa fever vaccine candidates: a scoping review of vaccine clinical trials. Trop Med Int Health. 2023;28(6):420–31.

Organization WH. World malaria report 2023: World Health Organization; 2023.

Fortes-Lima C, Schlebusch C. Closing the gaps in genomic research. Trends Genet. 2021;37(2):104–6.

Campbell MC, Tishkoff SA. African genetic diversity: implications for human demographic history, modern human origins, and complex disease mapping. Annu Rev Genomics Hum Genet. 2008;9:403–33.

Clarke E, Desselberger U. Correlates of protection against human rotavirus disease and the factors influencing protection in low-income settings. Mucosal Immunol. 2015;8(1):1–17.

Africa faces 470 million COVID-19 vaccine shortfall in 2021 WHO Africa [30 March 2024]. Available from: https://www.afro.who.int/news/africa-faces-470-million-covid-19-vaccine-shortfall-2021 .

A Breakthrough for the African Vaccine Manufacturing Africa CDC [20 Mar 2024]. Available from: https://africacdc.org/news-item/a-breakthrough-for-the-african-vaccine-manufacturing/#:~:text=The%20goal%20of%20the%20PAVM,30%20per%20cent%20by%202030 .

Declaration of Helsinki. http://www.med or jp/wma/helsinki02_j html. 1964;World Medical Association.

Integrated addendum to ICH E6(R1): Guideline for Good Clinical Practice E6(R2) International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) [27 Feb 2024]. Available from: https://database.ich.org/sites/default/files/E6_R2_Addendum.pdf .

Edwards IR, Biriell C. Harmonisation in pharmacovigilance. Drug Saf. 1994;10(2):93–102.

World Health Organization. Handbook for good clinical research practice (GCP): guidance for implementation. Geneva: World Health Organization; 2005.

Google Scholar

Al Khames Aga QA, Alkhaffaf WH, Hatem TH, Nassir KF, Batineh Y, Dahham AT, et al. Safety of COVID-19 vaccines. J Med Virol. 2021;93(12):6588–94.

Yao B, Zhu L, Jiang Q, Xia HA. Safety monitoring in clinical trials. Pharmaceutics. 2013;5(1):94–106.

Ozawa S, Stack ML. Public trust and vaccine acceptance–international perspectives. Hum Vaccin Immunother. 2013;9(8):1774–8.

World Bank. GDP per capita (current US$) - Gambia, The [30 Mar 2024]. Available from: https://data.worldbank.org/indicator/NY.GDP.PCAP.CD?locations=GM .

Rerimoi AJ, Jasseh M, Agbla SC, Reniers G, Roca A, Timæus IM. Under-five mortality in The Gambia: comparison of the results of the first demographic and health survey with those from existing inquiries. PLoS ONE. 2019;14(7): e0219919.

UNICEF. Gambia (GMB) - Demographics, Health & Infant Mortality - UNICEF DATA [19 March 2024]. Available from: https://data.unicef.org/country/gmb/ .

World Bank. Mortality rate, under-5 (per 1,000 live births) - high income [27 March 2024]. Available from: https://data.worldbank.org/indicator/SH.DYN.MORT?locations=XD .

Black RE, Cousens S, Johnson HL, Lawn JE, Rudan I, Bassani DG, et al. Global, regional, and national causes of child mortality in 2008: a systematic analysis. The Lancet. 2010;375(9730):1969–87.

Article Google Scholar

Barrow AAA, Azubuike PC, Cham D. Prevalence and determinants of acute respiratory infections among children under five years in rural settings of the Gambia: evidence from a national survey. GJEID. 2022;2(1):23–32.

Saha D, Akinsola A, Sharples K, Adeyemi MO, Antonio M, Imran S, et al. Health Care Utilization and Attitudes Survey: understanding diarrheal disease in rural Gambia. Am J Trop Med Hyg. 2013;89(1 Suppl):13–20.

Measuring the availability of human resources for health and its relationship to universal health coverage for 204 countries and territories from 1990 to 2019: a systematic analysis for the Global Burden of Disease Study 2019. Lancet. 2022;399(10341):2129–54.

World Bank. Adult literacy in the Gambia is lower among women than among men (2021) 2021 [16 Jan 2024]. Available from: https://genderdata.worldbank.org/countries/gambia-the/ .

National Review Report on Implementation of the Beijing Declaration and Platform for Action (BPFA) +25 UN Women [16 Jan 2024]. Available from: https://www.unwomen.org/sites/default/files/Headquarters/Attachments/Sections/CSW/64/National-reviews/Gambia.pdf .

Juffermans K, McGlynn C. A sociolinguistic profile of The Gambia. Socioling Stud. 2009;3(3):329–55.

World Bank. Individuals using the Internet (% of population) - Gambia, The The World Bank [24 Feb 2024]. Available from: https://data.worldbank.org/indicator/IT.NET.USER.ZS?locations=GM .

Campbell H, Byass P, Ahonkhai VI, Vella PP, Greenwood BM. Serologic responses to an Haemophilus influenzae type b polysaccharide-Neisseria meningitidis outer membrane protein conjugate vaccine in very young Gambian infants. Pediatrics. 1990;86(1):102–7.

Mulholland EK, Byass P, Campbell H, Fritzell B, Greenwood AM, Todd J, Greenwood BM. The immunogenicity and safety of Haemophilus influenzae type b-tetanus toxoid conjugate vaccine in Gambian infants. Ann Trop Paediatr. 1994;14(3):183–8.

Mulholland K, Hilton S, Adegbola R, Usen S, Oparaugo A, Omosigho C, et al. Randomised trial of Haemophilus influenzae type-b tetanus protein conjugate vaccine [corrected] for prevention of pneumonia and meningitis in Gambian infants. Lancet. 1997;349(9060):1191–7.

Leach A, Ceesay SJ, Banya WA, Greenwood BM. Pilot trial of a pentavalent pneumococcal polysaccharide/protein conjugate vaccine in Gambian infants. Pediatr Infect Dis J. 1996;15(4):333–9.

Cutts FT, Zaman SM, Enwere G, Jaffar S, Levine OS, Okoko JB, et al. Efficacy of nine-valent pneumococcal conjugate vaccine against pneumonia and invasive pneumococcal disease in the Gambia: randomised, double-blind, placebo-controlled trial. Lancet. 2005;365(9465):1139–46.

Bojang KA, Milligan PJ, Pinder M, Vigneron L, Alloueche A, Kester KE, et al. Efficacy of RTS, S/AS02 malaria vaccine against Plasmodium falciparum infection in semi-immune adult men in the Gambia: a randomised trial. Lancet. 2001;358(9297):1927–34.

Doherty JF, Pinder M, Tornieporth N, Carton C, Vigneron L, Milligan P, et al. A phase I safety and immunogenicity trial with the candidate malaria vaccine RTS, S/SBAS2 in semi-immune adults in the Gambia. Am J Trop Med Hyg. 1999;61(6):865–8.

Latunji OO, Akinyemi OO. Factors influencing health-seeking behaviour among civil servants in Ibadan. Nigeria Ann Ib Postgrad Med. 2018;16(1):52–60.

CAS PubMed Google Scholar

Hossain I, Hill P, Bottomley C, Jasseh M, Bojang K, Kaira M, et al. Healthcare seeking and access to care for pneumonia, sepsis, meningitis, and malaria in rural Gambia. Am J Trop Med Hyg. 2021;106(2):446–53.

Terefe B, Mulat B, Shitu K, Assimamaw NT. Individual and community level factors associated with medical treatment-seeking behavior for childhood diarrhea among the Gambian mothers: evidence from the Gambian demographic and health survey data, 2019/2020. BMC Public Health. 2023;23(1):579.

World Health Organization. Medical Product Alert N°6/2022: Substandard (contaminated) paediatric medicines: World Health Organization; [18 March 2024]. Available from: https://www.who.int/news/item/05-10-2022-medical-product-alert-n-6-2022-substandard-(contaminated)-paediatric-medicines .

World Health Organization. Guidelines for Registration of Traditional Medicines in the African Region WHO Africa [21 Feb 2024]. Available from: https://www.afro.who.int/publications/guidelines-registration-traditional-medicines-african-region .

O’Neill S, Gryseels C, Dierickx S, Mwesigwa J, Okebe J, d’Alessandro U, Peeters GK. Foul wind, spirits and witchcraft: illness conceptions and health-seeking behaviour for malaria in the Gambia. Malar J. 2015;14:167.

Okaiyeto K, Oguntibeju OO. African herbal medicines: adverse effects and cytotoxic potentials with different therapeutic applications. Int J Environ Res Public Health. 2021;18(11).

Chitturi S, Farrell GC. Herbal hepatotoxicity: an expanding but poorly defined problem. J Gastroenterol Hepatol. 2000;15(10):1093–9.

Kadiri S, Ogunlesi A, Osinfade K, Akinkugbe OO. The causes and course of acute tubular necrosis in Nigerians. Afr J Med Med Sci. 1992;21(1):91–6.

Haidara FC, Umesi A, Sow SO, Ochoge M, Diallo F, Imam A, et al. Meningococcal ACWYX conjugate vaccine in 2-to-29-year-olds in Mali and Gambia. N Engl J Med. 2023;388(21):1942–55.

Adigweme I, Akpalu E, Yisa M, Donkor S, Jarju LB, Danso B, et al. Study protocol for a phase 1/2, single-centre, double-blind, double-dummy, randomized, active-controlled, age de-escalation trial to assess the safety, tolerability and immunogenicity of a measles and rubella vaccine delivered by a microneedle patch in healthy adults (18 to 40 years), measles and rubella vaccine-primed toddlers (15 to 18 months) and measles and rubella vaccine-naïve infants (9 to 10 months) in the Gambia [Measles and Rubella Vaccine Microneedle Patch Phase 1/2 Age De-escalation Trial]. Trials. 2022;23(1):775.

Clarke E, Bashorun AO, Okoye M, Umesi A, Badjie Hydara M, Adigweme I, et al. Safety and immunogenicity of a novel 10-valent pneumococcal conjugate vaccine candidate in adults, toddlers, and infants in the Gambia-results of a phase 1/2 randomized, double-blinded, controlled trial. Vaccine. 2020;38(2):399–410.

James PB, Wardle J, Steel A, Adams J. Traditional, complementary and alternative medicine use in Sub-Saharan Africa: a systematic review. BMJ Glob Health. 2018;3(5): e000895.

Pacqué-Margolis S, Pacqué M, Dukuly Z, Boateng J, Taylor HR. Application of the verbal autopsy during a clinical trial. Soc Sci Med. 1990;31(5):585–91.

Breiman RF, Blau DM, Mutevedzi P, Akelo V, Mandomando I, Ogbuanu IU, et al. Postmortem investigations and identification of multiple causes of child deaths: an analysis of findings from the Child Health and Mortality Prevention Surveillance (CHAMPS) network. PLoS Med. 2021;18(9): e1003814.

Jiang F, Zhang R, Guan Q, Mu Q, He P, Ye X, et al. Immunogenicity and safety of a live attenuated varicella vaccine in children 1–12 years of age: a randomized, blinded, controlled, non-inferiority phase 3 clinical trial. Contemp Clin Trials. 2021;107: 106489.

Laursen SL, Helweg-Jørgensen S, Langergaard A, Søndergaard J, Sørensen SS, Mathiasen K, et al. Mobile diary app versus paper-based diary cards for patients with borderline personality disorder: economic evaluation. J Med Internet Res. 2021;23(11): e28874.

Mitsch JF. Bordering on national language varieties: political and linguistic borders in the Wolof of Senegal and the Gambia: The Ohio State University; 2016.

Fehr A, Nieto-Sanchez C, Muela J, Jaiteh F, Ceesay O, Maneh E, et al. From informed consent to adherence: factors influencing involvement in mass drug administration with ivermectin for malaria elimination in The Gambia. Malar J. 2021;20(1):198.

World Health Organization. Good Participatory Practice [30 March 2024]. Available from: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/global-research-on-novel-coronavirus-2019-ncov/solidarity-trial-of-covid-19-vaccines/good-participatory-practices#:~:text=Good%20Participatory%20Practice%20for%20Emerging%20Pathogens%20(GPP%2DEP)%3A%20a,emerging%20and%20re%2Demerging%20pathogens .

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Ikechuckwu Adigweme for substantial reviewing and proofreading

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Greater Good Science Center • Magazine • In Action • In Education

How to Stop Overthinking Your Happiness

All humans strive to be happy in some form. While there are intriguing variations in what exactly it means to be happy , this tenet is one of the rare human universals, transcending differences in culture, geographic location, age, ethnicity, and gender. As the Dalai Lama put it , simply, “The purpose of life is to be happy.”

That might lead to the expectation that we should all be happy, at least when circumstances afford it. Yet this is not the case. Even when people’s lives are good, many feel less than happy, and may be beset by anxiety and depression.

Thus there is a paradox: The pursuit of happiness is one of the prime values people hold, and they often fall short of attaining it. There might even be a further vexing twist on this happiness paradox, by which the more fervently people pursue happiness the further they get from it. In the words of the philosopher Eric Hoffer, “The search for happiness is one of the chief sources of unhappiness.”

The idea is that the more we value happiness the higher expectations we set for our happiness—high expectations we are more likely to miss. When we miss them, we may become disappointed and discontented. Such feelings are incompatible with happiness. And voila! Like in quicksand, the more we want to be happy, the less happy we become.

Fortunately, our research points to a solution—and the solution is pretty simple to state, if tricky to implement: When you’re experiencing something positive, don’t judge yourself.

How tracking happiness makes us unhappy

In earlier empirical research , we showed that intensely valuing happiness indeed seems to backfire. For example, people who endorsed statements like, “Happiness is extremely important to me,” were more likely to have lower well-being and greater depressive symptoms.

Intriguingly, this was especially the case when the circumstances of people’s lives were good. This is in line with the idea that the happiness paradox trap becomes engaged when expectations for happiness are activated—when we think everything is good and we ought to feel happy.

A recent New York Times opinion piece elaborates on the ways in which this happens, and puts its finger on one particular aspect of pursuing happiness that might interfere with attaining it: tracking it. It asked: “Could tracking happiness make us feel worse?” The answer to the question finds a resounding yes, it could and it does.

Tracking happiness may interfere with attaining happiness for two key reasons. First, when we track our happiness we are pulled out of the moment, which interferes with experiencing happiness to its fullest. This follows a suspicion memorably voiced by John Stuart Mill: “Ask yourself whether you are happy and you cease to be so.”

The second reason why tracking happiness might be harmful is that it invites comparison. And comparison—to our own high expectations, to other people’s blissful Instagram feeds—breeds discontent. This leads the happiness hunter directly into the place they wanted to avoid.

At this point, we might conclude that we should let go of our lofty goals to become happier. Maybe it is not in the cards for us and we should let go of the goal, and make do with whatever happiness scraps fall to us. But this conclusion does not accord with a large body of research that examines whether and how people can become happier.

Take, for example, UC Riverside psychologist Sonya Lyubomirsky’s research , which has found that Undermine Well-Being">happiness interventions can work in helping people be happier , at least sometimes. Meaning, when people want to feel happier, they can get there. The mystery is further deepened in that Lyubomirsky and her colleagues found this is especially true for people who are highly motivated and put forth more effort, as evidenced by selecting to be part of a happiness-enhancing intervention (compared to cognitive exercises).

Thus, there is a puzzle: How can valuing happiness be bad and pursuing happiness be good?

Roots of dissatisfaction

That puzzle led us to believe that the story must be more complicated. Perhaps valuing happiness—even intensely—is not inherently and always problematic. Rather, the problem might lie in how people approach happiness. There might be some bad and some good ways. That is, whether or not valuing happiness is associated with bad outcomes depends on the way in which people approach and think about happiness.

What might those ways be? UC Berkeley psychology alumni Felicia Zerwas and Brett Ford proposed a model of pursuing happiness that provides cues by taking a closer look at what happens psychologically when people pursue happiness. They proposed that it is OK to aspire to happiness, even intensely.

Where things start to get dicey is a bit further down the path where there is a fork in the road: On one path, someone can simply be OK with the level of happiness they have reached. But on the other path, someone can judge their experiences and worry about how much happiness they do or don’t have.

Going down this second path infuses negativity into their experiences, ultimately leading them further away from happiness. We can call this tendency concern about happiness. Concern about happiness, rather than simply aspiring to happiness, might lie at the heart of self-defeat.

The Science of Happiness

What does it take to live a happier life? Learn research-tested strategies that you can put into practice today. Hosted by award-winning psychologist Dacher Keltner. Co-produced by PRX and UC Berkeley’s Greater Good Science Center.

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Because this is a bit abstract, let us illustrate the two approaches with an example. Let’s say you are at a birthday party—your own! Your friends planned it for you and invited all your favorite people, who brought your favorite foods, treats, and beverages. You feel lots of positive emotion—contentment, excitement, gratitude, joy, and happiness. So far so good.

Now comes the key moment for our happiness hunter, where the path forks. On the one hand, you could simply aspire to being happy. Period. You enjoy the moment and dance the night away at your birthday party. End of story. On the other hand, however, you could be concerned about your happiness, adding judgment to your experience and with it a layer of overthinking. You have everything that should make you happy, and yet you wonder, you worry, This is perfect, why aren’t I happier? A disappointment sets in which might spiral into further disappointment.

Scientists call these “negative meta-emotions”: feelings we have about feelings. And so even when happiness is most within reach—or perhaps precisely because it is within reach—you get in your own way.

Now add to this the fact that few experiences are purely and unadulteratedly happy. Most events—even the best—have elements of ambiguity and mixed emotion. The cake might not be perfect or one of the guests might misbehave. We can easily see how the person who is concerned about happiness will latch on to those flies in the ointment and let them spoil the entire experience.

Four ways to not ruin happiness

So to recap, when people who aspire to happiness have positive events, they can simply roll with it and enjoy their experiences. Even if there IS a fly in the ointment, that’s OK. In contrast, when people who are concerned about happiness have positive events, they cannot simply enjoy them. They yuck their own yum: They judge and add negative meta-emotions.

That all means that the problem may not lie in how happy people are or how happy they want to be—it lies in how people respond to their happiness.

We put these ideas to an empirical test in a but Not Aspiring to Happiness Is Linked With Negative Meta-Emotions and Worse Well-Being">recent series of studies involving 1,815 participants from across the U.S. We found that, indeed, people fall into two types, with some scoring high on aspiring to happiness, and some scoring high on concern about happiness.

In our survey, they endorsed statements like, “I am concerned about my happiness even when I feel happy,” and, “If I don’t feel happy, maybe there is something wrong with me.” People who were more concerned about their happiness experienced lower satisfaction with their lives, lower psychological well-being, and higher depression symptoms.

And, based on diary entries they completed, we found that this link was explained by how they responded to positive events: they were more likely to have negative meta-emotions like disappointment about their own feelings. It’s like a slow drip of weak poison, where every single experience doesn’t harm overall well-being, but repeated instances over many months do.

Meanwhile, aspiring to happiness—considering happiness very important but without a tendency to judge—was innocuous and did not interfere with attaining happiness.

What does our research teach us about whether the pursuit of happiness is possible? We believe the studies point to a solution to the happiness paradox. From the concerned people, we can learn which pitfalls to avoid , and from the aspirers we can learn how to make happiness attainable. Four of these lessons are supported by science:

A first, most fundamental lesson is not to judge our emotions. As our walk through the process of pursuing happiness illustrates, the path to happiness goes awry when we judge . This is easier said than done, especially as judgments can be deeply ingrained. But it is possible to learn an accepting perspective: viewing our emotions, positive and negative, as natural and valuable parts of human life. Accepting our emotions, in turn, is associated with greater well-being . Acceptance can help us become happier and enjoy life more, and it also is a helpful strategy to be resilient when we encounter adversity.
Next, consider counteracting one of the main tributaries to judgment: monitoring how we feel. Monitoring itself is not harmful but it makes it a lot more likely that we will judge. When we don’t monitor our feelings, we are less likely to judge—and more likely to enjoy.
A third strategy unites the first and second, and it is: Don’t treat activities—or life—as a means to an end. If we can live our lives fully, mindfully, without looking beyond, true happiness might emerge. This idea is captured in a quote attributed to Nathaniel Hawthorne: “Happiness is like a butterfly which, when pursued, is always beyond our grasp, but, if you will sit down quietly, may alight upon you.”
Finally, if there is any common theme to research on what makes people happier, it is that social connection is helpful . This might be because social connection invites us to judge and monitor less and be in the moment more.

This is not to say the only paths toward happiness are psychological. Our cultures, systems, and societies play a key role in individual happiness . First, they directly create happiness. For example, giving people money , supporting social connection, and combating inequality and injustice are some of the best ways to make people happier. Second, they shape how people approach happiness . For example, we learn from our culture how to think about happiness and how to go about pursuing it, whether we simply aspire or are concerned.

Happiness is a—maybe THE—core value throughout human history and across cultures. While there are pitfalls, attaining greater happiness is possible.

About the Authors

Iris Mauss, Ph.D. , is the Thomas and Ruth Ann Hornaday Professor of Psychology and the director of the Institute of Personality and Social Research at the University of California, Berkeley. Her lab’s research focuses on emotions and emotion regulation, with an emphasis on their links to psychological health.

Brett Q. Ford

Brett Q. Ford, Ph.D. , is an associate professor of psychology at the University of Toronto, where she directs the Affective Science and Health Laboratory. Her research examines how people manage emotions and cope with stress, exploring both the benefits and the costs of striving to feel good.

You May Also Enjoy

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Why Americans Struggle to be Happy

How Much Control Do You Have Over Your Own Happiness?

Feeling Bad About Feeling Bad Can Make You Feel Worse

Is the Search for Happiness Making Us Anxious?

A Better Way to Pursue Happiness

Open access
Published: 04 September 2024

Answering open questions in biology using spatial genomics and structured methods

Siddhartha G. Jena 1 na1 ,
Archit Verma 2 na1 &
Barbara E. Engelhardt 3

BMC Bioinformatics volume 25 , Article number: 291 ( 2024 ) Cite this article

Metrics details

Genomics methods have uncovered patterns in a range of biological systems, but obscure important aspects of cell behavior: the shapes, relative locations, movement, and interactions of cells in space. Spatial technologies that collect genomic or epigenomic data while preserving spatial information have begun to overcome these limitations. These new data promise a deeper understanding of the factors that affect cellular behavior, and in particular the ability to directly test existing theories about cell state and variation in the context of morphology, location, motility, and signaling that could not be tested before. Rapid advancements in resolution, ease-of-use, and scale of spatial genomics technologies to address these questions also require an updated toolkit of statistical methods with which to interrogate these data. We present a framework to respond to this new avenue of research: four open biological questions that can now be answered using spatial genomics data paired with methods for analysis. We outline spatial data modalities for each open question that may yield specific insights, discuss how conflicting theories may be tested by comparing the data to conceptual models of biological behavior, and highlight statistical and machine learning-based tools that may prove particularly helpful to recover biological understanding.

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Introduction

The invention of the microscope allowed for unprecedented glimpses into the micron-scale world, and led to the first characterizations of the cell [ 1 ]. A subsequent push to discover the constituent components of the cell led to the development of modern biochemical methods, predominantly based around density centrifugation or chemical separation. In this process, cells and tissues are dissociated and then separated by density to study the subcellular interactions between individual biopolymers. This approach progressively revealed the “parts list” of the cell, illuminating the composition of cellular structures such as the rough and smooth endoplasmic reticulum [ 2 ] and the Golgi body [ 3 ]. These methods, however, lost the spatial context of where biopolymers were located in the cell, not to mention the relative locations of the cells themselves.

Imaging and biochemical characterization of cells and tissues have both made incredible progress since their initial development. Advances in physics in the second half of the 20th and early 21st century led to the invention of the electron microscope [ 4 ], scanning tunneling microscope [ 5 ], atomic force microscope [ 6 ], and super-resolution microscopy [ 7 ]. Together with fluorescent proteins and affinity reagents (such as increasingly specific antibodies), these instruments opened a new frontier of molecular-level imaging. Scientists could interrogate the spatial location of different proteins, nucleic acids, or lipids within a tissue sample, and associate their distribution with particular cell morphologies or phenotypes.

The development of high-throughput genomic sequencing technologies in the early 21st century led to the characterization of biology at base-pair resolution, first with bulk tissue samples as input, and later within single cells [ 8 , 9 ]. These protocols revealed the molecular composition of nucleic acids within tissues and cells, but without the spatial or visual context of imaging, since these methods required lysing cells to extract nucleic acids for sequencing.

The parallel technologies of sequencing and imaging have continued to increase in quality and resolution, and have complemented one another in important biological findings. A common post-hoc structure for leveraging the two approaches is to use statistical methods to identify correlations between an imaging-based readout and a sequencing-based readout [ 10 ], or predict gene expression levels in a sample using histology imaging [ 11 , 12 ]; one such example is the mapping of somatic mutations, such as those found in cancer, to a cellular phenotype such as the emergence of dense cancerous tissue that is easily identifiable in pathology imaging [ 13 ]. More recently, pairing the two measurements in the same sample has become possible as biochemical methods to study genomics have expanded into the spatial realm. Fluorescence in situ hybridization (FISH) methods involve probes that directly bind to proteins, RNA, or DNA of interest, allowing them to be imaged while preserving the location of the biomolecule [ 14 ]. Alternatively, cells from a particular region of a tissue section can be sequenced together and reassigned to the tissue image afterwards, providing a coarse-grained view of cell-based gene expression across the tissue. Cells may also be optically barcoded prior to sequencing assays to capture their relative location. Using these methods, the high-dimensional genomic state of a single cell can be measured, and the cell can subsequently be mapped back onto its position in its native context, whether in culture or embedded in a tissue [ 15 ]; both cellular state and cellular environment is explicit in these approaches.

Spatial genomics have already been used in a number of contexts to characterize genome-wide changes associated with cellular differentiation, development, interventions, and the progression of diseases such as cancer [ 16 , 17 , 18 ]. With this new genome-scale spatially-resolved readout, researchers have the opportunity to discover general principles that govern cellular behavior in their environmental contexts. As better experimental methods are developed, of equal importance are the analytic frameworks that we use to understand and interpret the resulting spatial data.

In this review, we take a look at the types of questions to which scientists may apply spatial technologies, with an eye towards the methods appropriate for analyzing experimental results in the context of open questions in cellular biology. We first summarize the different spatial scales of analysis: molecular-, cellular-, and tissue-level data resolutions. We then examine four open questions that may be answered using spatial genomics:

What is the functional spatial effect size of a cell?

How do cell state and expression profile interact with cellular morphology, movement, and behavior?

What local effects shape clonal dynamics in dividing and differentiating tissue?

How does a cellular environment shape rare events?

We review current and potential methods for answering these questions from spatially-resolved genomic data. As the suite of spatial genomics tools expands, we hope that the approaches discussed here may be generalized to a broad collection of robust, usable tools and data resources.

Spatial scales of biology

Distinct scales of organization at different parts of the body. Subcellular localization of receptors, cytosolic proteins, and signaling molecules affects cellular communication between neurons, B and T cells, or cardiac muscle in the heart. Each of these cell types is, further, a components of multicellular assemblies of many neurons, immune cells in the bloodstream, or heart tissue

Peer through a microscope at a slice of tissue on a slide, and a wide range of cell shapes, sizes, and patterns present themselves. Further antibody staining reveals the location of proteins in specific intracellular compartments and throughout the extracellular matrix [ 19 ]. A tissue sample contains biological processes occurring at three scales: subcellular processes taking place within a subcompartment of a single cell, cellular processes taking place within $1-~10$ cells, and multicellular processes taking place among $>10$ cells (Fig. 1 ). At the subcellular scale, our questions primarily involve interactions between individual molecules in organelles or membranes. At the cellular level, we ask questions about the overall composition of the cell and interactions with nearby cells. Finally, at the multicellular level, we ask how groups of cells of different types come together to form tissues with multifaceted functions. The scales described here map neatly onto the paradigms of autocrine, paracrine, and encodrine signaling that are common parlance in physiology; however, we hope that generalizing these terms to their relevant length scales may lead to deeper insights about systems not currently or commonly studied in medicine.

I. Subcellular resolution

What molecules are in an individual cell and where do they function? Nucleic acids and individual proteins are largely the drivers of cellular morphology and behavior. Using specific affinity reagents, such as antibodies or oligonucleotide probes, one can identify specific RNA and protein species in a fixed sample, providing insight into function. These molecules are often complexed together; one such example is chromatin, which consists of DNA, histone proteins, and often associated RNAs [ 20 ]. Here, we will describe some of the promising use cases for investigating these molecules at subcellular resolution.

DNA: Accessibility and structure

DNA acts as the biological blueprint for an organism. With the exception of somatic mutations [ 21 ], cells across an organism largely share the same DNA, yet serve vastly different functions. This functional heterogeneity is made possible through epigenetic modifications, which control the genes that are transcribed or repressed in a cell [ 22 ]. Structural changes from epigenetic modifications such as DNA or histone methylation [ 23 , 24 , 25 ] can lead to differentially accessible regions along the length of the genome. These exposed chromatin regions, which may be read out through methods such as ATAC-seq [ 26 ], allow binding of regulatory molecules such as transcription factors and RNA polymerase, leading to transcription. Other modifications, such as histone acetylation, can lead to recruitment of specific transcription factors and result in gene expression [ 22 ].

Although distinct chromatin modifications have been associated with transcriptional activation or repression, the spatial organization of the genome and its link to the expression of specific programs remains less clearly defined. The genome is spatially partitioned, in structures largely driven by these epigenetic modifications, into domains of active or inactive genes called A and B compartments, respectively [ 27 ]. Although chromatin conformation capture methods such as Hi-C are able to capture these compartments [ 28 , 29 ], the link between these compartments and their transcription products is still being uncovered on a spatial level within intact cells. What occurs on the border between A and B compartments? Are there features that further distinguish different genomic compartments? A deeper understanding of spatial genome organization and its effect on the transcriptome would provide answers to these questions, as well as potentially addressing epigenetic dysregulation, which has been implicated in aging, response to environmental exposures, and disease progression [ 30 , 31 ].

RNA: Diversity and function

Given the (generally) shared DNA sequences across cells from a single organism, variation in RNA expression is a major driver of cellular variation. Different cell types and cell states show different patterns of RNA expression, but RNAs spatially confined to compartments in the nucleus or cytoplasm are difficult to capture through conventional RNA sequencing. This is of particular interest since the dynamic organization of mRNAs may produce differential protein gradients in a tissue, driving processes such as metabolic regulation [ 32 ], polarization during embryonic development, or synapse formation in neurons [ 33 , 34 , 35 ]. Beyond mRNAs, a number of noncoding RNAs (ncRNA), such as long noncoding RNAs (lncRNAs) and microRNAs (miRNAs), have been identified and found to have important regulatory functions [ 36 ]. Understanding the relationship between ncRNA function and their localization in specific nuclear and cellular compartments, combined with absolute transcript levels, would provide a more complete characterization of the transcriptional state of single cells [ 37 ]. Outside of the cell, RNA in extracellular vesicles may be implicated in inter-cellular signaling [ 38 ]. Spatial transcriptomics provides previously unavailable insights that will further scientists’ understanding of these RNA molecules.

Proteins: localization, abundance, and modifications

When possible, protein measurements provide the most direct window into active cell function. While the prevailing view is that transcript levels correlate with protein levels, possible discrepancies may arise between the two [ 39 , 40 ], which may necessitate direct measurement of protein levels depending on cellular context [ 41 , 42 ]. Inferring protein levels from transcript levels also ignores aspects of protein regulation such as localization or post-translational modifications that may activate, modify, or suppress protein function [ 43 ]. Antibodies to common protein modifications have allowed scientists to visualize cell processes such as signaling, while more extensive spatial measurements allow for mapping of specific versions of proteins to subcellular locations within individual cells. Once localization of a particular protein or protein family is established, further analyses such as proximity biotinylation [ 44 ] or affinity purification mass spectrometry [ 45 ] may be performed in the same sample, allowing for deeper insights as to what tasks the protein was performing in its targeted location.

II. Cellular resolution

Complex life is dependent on the cooperation and communication between many diverse cell types. Cell types are often categorized based on their interactions with other cells and tissues: for instance, neurons transmit signals to one another to form the basis of cognition [ 46 ], T cells identify and kill foreign cells [ 47 ], and cardiomyocytes coordinate signaling between themselves to drive pacemaker activity in the heart [ 48 ]. Recent advances in high-throughput single-cell measurements allow us to survey this diversity of cell types and interactions from a transcriptional or protein expression perspective.

Variation also exists within cell type, often inelegantly lumped into the vague term cell state . For instance, although a population of T cells are likely more similar to one another than they are to a muscle cell or skin cell, individual cells or subsets within the T cell population may be in different states of proliferation, activation, or quiescence at any given moment [ 47 ]. Cell states are controlled in part by local interactions between T cells and their environment, causing their transcriptomes and functional responses to diverge [ 39 , 49 ]. Even in the absence of different environments, there are many subtypes of T cells each with their own cell state profile, and moreover cell states possess a natural level of variation within a population [ 49 , 50 ]. Some of this variation is due to the stochastic nature of reactions such as transcription or chromatin dynamics occurring in single cells [ 51 ]. However, it is an open question how much of heterogeneity is random and how much is a byproduct of factors that are not measured in transcriptomic studies, such as interactions at the spatial boundaries of the cell population [ 51 , 52 ].

Cells function together, so questions at the cellular scale must consider the interactions with individual cells in a local neighborhood. Receptor-ligand interactions that activate biochemical signaling pathways allow cells to modulate the transcriptomic state of nearby cells [ 53 ]. Cells from the same organisms may work together to perform complementary functions, like Schwann cells coating astrocyte neurons with myelin sheets to improve cell-to-cell signaling [ 54 ]. Cells from different organisms may also compete in the same tissue; for instance, immune cells fighting an infection or autoimmune diseases [ 55 ].

III. Multicellular resolution

In multicellular organisms, groups of many heterogeneous cells come together to form cellular complexes, tissues, and organs. Repeating patterns of multiple cell types in close proximity in a tissue are referred to as cellular niches [ 56 , 57 , 58 , 59 ]. Beyond the identification of the cell type composition of a particular niche, there is considerable interest in understanding niche sizing, the variation in niche architecture, the developmental trajectory of niches, and the interactions between niches [ 60 , 61 ]. For instance, stem cell niches are of particular interest as they possess the potential to regrow and regenerate specific tissues [ 62 ].

Collections of niches create tissue architectures, and spatial transcriptomics presents the opportunity to bring more context to the organization of tissues from a molecular lens. How a repeated niche differs across the tissue may be explained by chromatin modifications or differences in RNA and protein expression, which lead to cell-type heterogeneity. Differences in structure from genetic defects can be explained causally by linking mutations to specific changes that propagate across the tissue [ 63 ].

The ambitions of single-cell studies have grown from defining distinct cell types [ 64 ] to the creation of comprehensive atlases— from the tissue level [ 50 , 65 ] to organs [ 66 , 67 ] to full organisms [ 68 , 69 , 70 ], across age [ 71 , 72 ] and disease status [ 73 , 74 , 75 , 76 , 77 ]. These atlases have the potential to advance biological discovery, in particular because they may provide a more thorough description of the distinct cell states in a larger population. Future work projecting single-cell atlases to spatial scales will add more context to these cell states, providing insights into the organization of specific cell states, cell types, and cellular niches in tissues and organs.

Key questions in spatial biology

I. what is the functional spatial effect size of a cell.

Four key questions in spatial biology. I. Cells can release ligands that allow them to communicate with Other cells across various, unknown spatial scales. II. Cell location can affect morphology, movement of cells within a tissue and gene expression in unknown ways. III. It remains unclear how dividing clonal cells distribute within a tissue, and how this spatial distribution affects dynamics of gene expression. IV. It remains unclear how rare events in gene expression are influenced and orchestrated in within a tissue

In a multicellular context, cells use many modes of communication to convey messages to their surroundings (Fig. 2 , Question I). The mechanisms by which and extent to which cells are able to communicate across the body has long captivated biologists. The concept of morphogens —hormones that enable cellular communication over distance—is an old one [ 78 ]. As biochemical tools grew more sophisticated, numerous signaling molecules and pathways were found to serve this critical role [ 79 , 80 , 81 , 82 ]. These signaling pathways, which are often conserved across organisms, continue to inform research today; for example, live-cell imaging revealed that the Ras/ERK pathway propagates waves of signaling activity during development in response to processes within the cell as well as directing events such as wound healing that take place outside of the cell [ 83 , 84 , 85 ]. As we piece together the toolbox of molecules used for cellular communication, it remains unclear how to best measure coupling between cells in a tissue. For a given cell, how do we know how much of its behavior is due to communication with cells around it? How far does this communication reach?

Biophysical models of cell interactions form a useful framework within which to ask these questions. Perhaps the earliest of these models is the the French Flag Model of morphogen gradients, where particular levels of a molecule are mapped to distinct outcomes in a tissue. Results from this model provided a conceptual explanation of how diffusing gradients of such a chemical could result in patterning along the length of a developing embryo. This class of model led to more mathematically sophisticated descriptions of cellular interactions, including the Turing model, which describes pairwise interactions between two molecules that are capable of generating stable patterns in a tissue [ 86 ]. In these early models, the parameters of interest were (i) the geometry of the tissue, (ii) the level of morphogens in space and time, (iii) the feedback, feed-forward, or cooperative interactions occurring between morphogens in space, and (iv) the effects of these morphogens on cell state.

As more interesting biological patterning questions emerged, modeling these behaviors expanded accordingly. Ising models—spin models based on a lattice-structured Markov random field adapted from statistical physics—were used to model cellular interactions [ 87 ]. Kuramoto oscillators model coupled cells with continuous states to drive phase differentiation [ 88 ]. Alternatively, information-theoretic approaches have been used to understand how small sets of signaling genes encode a rich space of spatial architectures from experimental data, combining mathematical biophysical models with experimentally collected data [ 89 , 90 ]. All of these modeling paradigms capture the key components of cell connectivity, morphogen levels, and morphogen interactions.

Spatial sequencing provides a high-dimensional dataset (Fig. 3 ) to statistically identify the genes involved in intercellular communication in different contexts. Early analysis has focused on identifying and building on known ligand-receptor pairs. In the analysis of the initial seqFISH+ results [ 91 ], the authors looked for enrichment of expression of known ligand-receptor pairs in adjacent cells by comparing against a null expression distribution created by permutation shuffling. On the same data, graph convolutional neural networks were trained to predict the probability of two genes interacting given the spatial neighbors graph and expression of the two genes in each cell [ 92 ]; known ligand-receptor pairs were used as positive and negative examples. Optimal transport methods were used to identify similar distributions of known receptor and ligand expression patterns in spatial data [ 93 ], which captured potential interactions beyond spatially-adjacent cells.

Essential cellular behaviors assayed in spatial genomics. Distributions of RNA ( A ), cell type clustering from gene expression ( B ) and spatial correlations ( C ) can all be measured from spatially resolved sequencing data

Although limiting analysis to known receptors limits the investigator’s ability to discover new signaling motifs, testing pairs or higher-order sets of genes for interactions leads to a combinatorial increase in statistical tests and computational demands. Few experiments have sufficient sample size to adequately power investigations of higher-order interactions. Instead, statistical methods often jointly model all genes together and try to learn subsets of co-varying genes that are associated with spatial patterns. For example, Gaussian process regression can model spatial gene expression with clever kernel composition [ 94 ]. Three kernels are used to decompose gene expression variance into intrinsic cell effects, extrinsic or environmental effects, and cell-cell interactions. Comparison to a null model assuming no cell-cell interactions identifies communication-related genes. Related work reconstructs gene expression from given cell-type labels and spatial neighbor graphs using autoencoder architectures [ 95 ]. While not explicitly using the expression levels of other genes, the cell-type label serves a similar role in capturing expected nonspatial gene-gene correlations. This work similarly uses a null model without spatial connectivity to test for interacting genes. For both strategies of testing pairs of genes or a gene against all other genes, the number of tests done requires proper null models, multiple hypothesis testing correction, and a reliable way to control for known cell-type heterogeneity and adjacency, which may bias results.

Single snapshots of spatial expression data sets miss important information on the temporal nature of signaling. Parameters such as the responsivity of a cell type to a particular protein, or the pairwise interactions between two genes, may change as a function of time. For example, spatial measurements at two stages of uterine development were used alongside CellPhoneDB [ 96 , 97 ], a database of know ligand pairs, to identify which cell types had compatible signaling proteins and were likely to be in communication during development [ 98 ]. Increasing the resolution of time points will allow the expansion of such statistical techniques to identify interactions over time. Time-series analyses can also help identify more causal relationships in signaling. Fluorescent live-cell imaging data and point-process models were used to quantify ERK signaling and downstream Fos expression under different drug treatments [ 99 ]. Specifically, self-exciting Hawkes processes model expression and signaling among cells over time and space. Newer fluorescence imaging protocols will expand the number of behaviors that can be captured simultaneously in live-cell imaging data [ 100 ].

Understandably, we currently have the most confidence in interactions between directly adjacent cells, since long-distance channels or indirect secretory pathways through which cells can send or receive messages are more difficult to study. By incorporating multiomic measurements of cells in space, as well as potentially integrating time-resolved measurements, we may be able to better understand cell communication at a distance.

II. How do gene expression profiles interact with cellular morphology?

A common practice in both basic cell biology and pathology is to use cell morphology to distinguish cell types or states. Cellular structure informs function, and thus cells from different tissues and different cell types in a single tissue vary markedly in their appearance (Fig. 2 , Question II). For instance, due to dysregulation in growth pathways, cancerous cells are commonly larger than their healthy counterparts, and are often more motile when imaged over time under a microscope. Physical stress can also change cell state and gene expression; mechanical stretching of fibroblasts was found to dramatically alter their epigenome states to enable cells to prevent damage to the physical structure of the genome [ 101 ].

Before spatial single-cell technologies, some methods attempted to jointly model morphology patterns and gene expression from paired bulk tissue samples [ 10 , 102 ]. The limitation here is the mismatch between resolutions: Images can provide cellular-level phenotypes, but bulk expression cannot. The emergence of spatial single-cell measurement techniques is poised to overcome this limitation.

One open question is how to best represent cellular morphology. While gene expression is conventionally represented by a count matrix, there is not a similar universal tabular form to represent cellular morphology. Recent approaches have attempted to provide solutions to this problem. One strategy is to convert morphological data, generally in the form of images, into tabular data of derived features. One study measured gene expression with the L1000 assay and morphological features such as nuclear area or DNA organization using the Cell Painting assay [ 103 ]. Lasso logistic regression and a multi-layer perceptron accurately predict gene expression from $\sim$ 1000 morphological traits provided by CellProfiler [ 104 ]. CellProfiler was also used to create tabular readouts from paired imaging and single-cell CRISPR-Cas9 knockouts, in order to cluster gene knockouts with similar morphological changes and build genetic interaction networks [ 105 ].

An alternative approach is to use neural networks to capture the features of an image. For example, MorphNet uses a variational autoencoder to encode the cell state into a lower dimension, and a generative adversarial network (GAN) [ 106 ], which jointly optimizes two neural nets–one to generate imaging samples from the encoded gene expression that look like real imaging data, and the other to predict whether the generated imaging sample is real or fake—in order to predict cellular morphology from gene expression in brain-wide MERFISH data [ 107 ]. A recent study collected a paired CRISPR knockout and imaging dataset, as in related work [ 105 ], but calculated embeddings of images from a self-supervised vision transformer trained on single-cell Cell Painting images [ 108 ]. This approach outperformed classic image featurization for classifying single CRISPR perturbations’ mechanism of action and recovering known biological relationships between genes [ 108 ].

Each approach to study the relationship between cellular morphology and cell state has different strengths and limitations. Individual features derived from cell painting methods are easier to interpret and can be used in small sample size regimes. Tabular data is amenable to traditional statistical regression methods and the accompanying theoretical guarantees; however, count data and specific experimental designs often require additional structure on the methods that are challenging for non-statisticians. Neural networks provide more flexibility in the morphological variation that they capture, but require both an adequate amount of data for training and some expertise in training and interpreting the models. Both approaches also require identifying which variable should be the output and which variable should be the input.

Biologically, cell morphology and movement are determined largely by membrane contacts; cell membranes are predominantly composed of lipids and proteins, and the abundances of these components are largely dictated by gene expression. However, changes in morphology and motion also drive changes in gene expression as the cell responds to new conditions. Many signaling pathways begin with external influences on membrane proteins. These feedback loops suggest the causal relationship goes both ways, limiting static data to providing mostly correlative findings.

In the near future, decreases in costs and improvements in resolution will allow scientists to better establish the causal relationships between gene expression and morphology. Time-series measurements and live-cell imaging can uncover the temporal ordering between gene or protein expression events and morphological changes. Single molecule tracking will be able to resolve where in the cell proteins are functioning and creating structural features [ 109 ]. These improvements will shine further light on the relationship between morphology, motion, and function. With improved experimental methods and proper statistical techniques, a complete understanding of the determinants of cell morphology is within grasp.

III. What local effects shape clonal dynamics of dividing and differentiating cells?

Cell division establishes populations of clones in various tissues around the body (Fig. 2 , Question III). Cell division may maintain genomic, transcriptomic, and epigenomic information, but comes with the downside of passing on potentially deleterious properties such as DNA mutations and aberrant epigenomic states. On the other hand, precise maintenance and expansion of particular clones underlies important processes such as the development of adaptive immunity. Some biological processes are “bottlenecked” in the sense that unfit clones die out due to physiological conditions [ 110 ]. However, many cell populations, including hematopoetic stem cells that give rise to the entire lineage of circulating blood cells, are comprised of hundreds or thousands of clonal populations, including clones that harbor mutations that decrease proliferation [ 111 ], suggesting that clonal heterogeneity may be the rule rather than the exception.

Biophysical models of clonal dynamics have been studied for many years in the context of stem cells. A primary question for any stem cell population is whether and how the population replenishes. This has been modeled by three parameters representing three distinct probabilities of division outcomes for a stem cell: (1) division into two stem cells, (2) two differentiated cells, or (3) one stem cell and one differentiated cell [ 112 , 113 ]. Recently, another intriguing possibility has been introduced: rather than remaining in static states, cells may stochastically transition between stemlike and differentiated states with some probability, only fully converting to a distinct fate when faced with a particular signal [ 114 ].

These relatively simple “state transition” models, applied to well-mixed or spatially structured populations, have been used to great effect to predict behavior of stem cell populations. Crucially, certain regimes representing distinct probabilities of differentiation or division can be distinguished from one another experimentally through the resulting predicted distributions of clone sizes. One early method for marking clones involves dosing subsets of cells with a dye that subsequently becomes diluted over time, a method that is commonly used to monitor T cell proliferation [ 115 ]. While this can accurately mark the generation, it does not provide direct linkage across generations. Another method involves inducing fluorescent protein expression in a subset of cells, using this to identify groups of fluorescent cells that all originated from the same clone. Similarly, this approach does not allow for identification of mother-daughter cell relationships, but can be used to measure clone size distributions by quantifying the size of distinct groups.

Experimental methods to identify mother-daughter relationships between single cells within a clonal population, on the other hand, were difficult until CRISPR-Cas9 was developed. DNA-based barcodes for clonal tracking are an attractive technological development towards addressing clone-related questions. Static barcodes can be introduced into the genomes of cells in a random fashion, so that some distribution of barcodes is introduced into the first generation and subsequently passed on to each cell’s progeny [ 116 , 117 ]. Through subsequent DNA sequencing, the barcode for each cell can be recovered to establish clusters of cells that arise from the same clone. More recently, dynamic barcoding can be used to establish precise lineages: in this method, CRISPR-Cas9 randomly edits a barcode as it is passed on from cell to cell, allowing researchers to reconstruct lineages through the introduction of random SNPs [ 118 , 119 ].

Combining imaging-based methods with barcoding offers an opportunity to build models of clonal expansion in a spatial context. In particular, work extending clonal dynamics models to the mammalian epidermis exposed complex emergent clonal behavior that arises when cells are confined to a tissue [ 112 , 113 ]. The epidermis is highly stratified, and, within a layer, clonal populations of stem cells can often be visualized as spatially defined clusters of mitotically active or inactive cells. Post-mitosis, differentiated cells that arise from a stem cell on a basal layer will often emerge on a suprabasal layer, giving rise to complex geometries of clone dispersion spanning three dimensions [ 120 , 121 , 122 , 123 ]. Specific functional geometries of tissues, such as the crypts of the stomach or the cylindrical structure of vasculature, likely involve similarly unique geometric patterning of clones.

We expect that interrogating clonal populations in their native tissue through a combination of imaging, barcoding, and transcriptomics will allow for a broader range of clonal behaviors to be defined. In particular, although clonal populations tend to be “coarse-grained,” as observed in the epidermis as well as in metastatic clones using spatial DNA sequencing [ 18 ], it remains to be seen how fluid individual clonal populations are within a tissue.

Are there definable subclones within a clone that occupy their own spatial niche? In the case of cancers, cells from one clone may metastasize to form their own population elsewhere. In what ways is this subclone distinct from the original? Prior work used variance decomposition of Slide-seq data to identify gene signatures that explained differences between distinct clones as well as subclones within cancerous tissue [ 124 ]; similarly, constrained regression and covariance estimation were used to study clonal populations using copy number variation [ 125 ]. Related work jointly identified copy number polymorphisms in spatial transcriptomics and inferred cellular clones in tissues using a hidden Markov random field [ 126 ]. Extending spatial experiments using dynamic barcoding would allow for fine-grained resolution of subclone emergence in the future; analytic methods to reconstruct the full clonal trajectories would add specific mother-daughter relationships in space.

IV. How does a cellular environment shape rare events?

The first single-cell RNA-seq datasets confirmed what many biologists had already suspected: that substantial expression heterogeneity exists between cells in a tissue, and that this heterogeneity underlies a wide range of diseases. For instance, cancers often arise not as a function of cellular collectives, but as a function of one particular cell. A dominating paradigm in cancer is that single cells experience a perfect storm of factors that lead to them becoming jackpot cells , or clones that express a specific mRNA at extremely high levels while their sister clones express none [ 127 ] (Fig. 2 , Question IV). In some cases, these rare cellular states are transient; jackpot cells may not always express combinations of genes throughout their lifetime, and may not pass on their phenotypes to their progeny. In BRAF melanoma, jackpot cells fail to follow Luria-Delbruck behavior and do not pass on their properties unless challenged with the addition of a drug, which then stably locks in the resistant state [ 127 ]. This implies that every time a population of cancer cells is challenged with a drug, a constant but small fraction of the population experiences stochastic resistance. Other rare cellular phenotypes are more consistent with Luria-Delbruck dynamics; for instance, rare mutations causing cancerous growth are passed on from mother cell to daughter cell to create large colonies and eventually solid tumors [ 128 ].

While we are beginning to understand the factors affecting jackpot cell emergence in culture, the environmental factors (e.g., tissue niche, surrounding cellular milieu, position in the tissue) that regulate the cell states giving rise to heterogeneous gene expression events are still unknown. Leveraging spatial genomics to identify these rare events such as jackpot cells among other cells in a tissue may lead to a better understanding of these rare events. However, a major limiting factor in studying such rare events is statistical confidence in detecting such events. In studies performed on melanoma cells, jackpot cells were detected using RNA-FISH with probes targeting a pool of pre-identified drug resistance genes [ 127 ]; this allows for high-confidence calls of jackpot cells that may not be possible in standard single-cell sequencing workflows. The total number of mRNA transcripts per cell is typically much lower than the mRNA counts collected using FISH methods, especially in such a small pool of target genes. In this particular case, bulk RNA-seq was used to identify a set of high-confidence genes for RNA-FISH probing. However, the candidate genes designating jackpot cells may not always be so well defined, and using a sparse readout such as single-cell transcriptomics to identify novel jackpot cells presents a circular problem.

Methods opportunities in spatial biology

Methodological opportunities for spatial genomics. We describe distinct “classes” of biological and biophysical measurements that fall within our four key areas of interest. These include diffusion of RNA away from the site of transcription, establishment of patterning in a multicellular tissue or organism, and gene regulatory networks giving rise to particular behaviors. For each, we describe how the underlying processes may be directly measured, or indirectly inferred, from spatial genomics data

These four open questions in spatial biology—along with the existing or forthcoming technologies to observe the corresponding biological phenomena in tissues—require the development of statistical approaches to arrive at precise and reproducible answers. The opportunity here is in building models that incorporate additional structure—time, space, or environmental context. Here, we outline opportunities for methods development in each of the four areas, focusing on methods that are most likely to be successful given the constraints of the data and sample size (Figure 4 ).

To illustrate the structure of potential novel and existing methods, we assume that we start with one of two structured datasets. The first dataset is two tables, a cell by gene (or other feature) count matrix $X \in \mathcal {R}^{N \times G}$ and cell by spatial coordinate matrix $C \in \mathcal {R}^{N \times D}$ , where N is the total number of cells assayed, G is the number of genes assayed, and D is the number of spatial dimensions (this will generally be 2 or 3). We will use $x_{i,j}$ to refer to the count of gene j in cell i , $x_{i,-j}$ to represent the gene counts in cell i of genes other than j , $x_i$ to refer to the vector of all gene counts in cell i , and $x_{-i}$ to refer to all gene expression in cells other than i , with similar subscripts for the coordinates.

Alternatively, we may have a more granular set of observations of the identity of each of M molecules observed (e.g., spatially localized RNA transcripts), with a location for each molecule $c_m \in R^{D}$ , and the cell it belongs to $o_m \in {1,2,\dots ,N}$ . We will use $c_i$ to loosely refer to the coordinates of all molecules in cell i and $m_i$ for the identity of all molecules in a cell i . In the following section, question-specific data and notation will also be introduced to illuminate the modeling approaches proposed. For each opportunity, we try to identify challenges across data collection, model architectures, and model inference and evaluation.

I. Methods to characterize the functional spatial effect size of a cell

A spatial experiment observes an instance from some distribution over the expression and spatial coordinates of the cells, p ( X , C ). Signaling between cells implies there is some conditional relationship of a cell’s state on other cell’s state. A model to identify spatial signaling assumes that the variability of cell state can be decomposed into factors from other cell states ( extrinsic factors ) and cell-specific factors ( intrinsic factors ) [ 129 , 130 ]. This may look like a model with form:

where $\epsilon$ is some noise distribution. We use $f_1$ to represent how cellular state feature j is dependent on the other state features in the cell (i.e., intrinsic factors). Often, cell type is used as a proxy for intrinsic cell state. Methods for dimension reduction, such factor analysis, fit without spatial information can also be used to find the intra-cellular covariance between features of cell state.

Next, $f_2$ represents a spatial pattern of cell state that is a function of location but not environment. This variability may reflect some global architecture of cell types and niche organization. It accounts for variation in cell state that is not part of the signaling pattern that we are attempting to find. For example, a tissue sample might be organized with different cell types separated in distinct regions of space, which creates a spatial pattern of gene expression that is not the result of short term signaling behavior. We can think of a model like nonnegative spatial factorization [ 131 ] as decomposing the variance among these two terms: non-spatial factors capture the intra-cellular covariance while spatial factors learn the spatial archetypes for each feature of cell state.

The final term, $f_3$ , represents perhaps the most interesting behavior—the dependence of cell state on local cells. We are looking for repeated patterns of variation in cell state that cannot be explained by the other features in a cell or by global patterns of expression. Of critical importance is correctly teasing out this relationship from our spatial term $f_2$ . This can be done by restricting the cell’s dependence to only neighboring or nearby cells, making $f_3$ represent the unique local covariance of gene expression.

As observed before, spatial factor models tend to capture only the first two functions while missing local signaling effects [ 131 , 132 ]. Looking at the correlation between known ligand-receptor pairs expression across neighbors uses cell type to control for the effects $f_1$ and proximity to zero out $f_2$ , testing specifically for the existence of $f_3$ .

Thus the opportunity remains to fully model all three factors simultaneously. Data with distinct local and global signals are essential for a model to learn the desired patterns. The appropriate functional forms of each term will be required to accurately capture biological processes; nonlinear functions will likely be necessary for an accurate model, although they will increase the difficulty of inference and also the data requirements for adequate power. For $f_3$ , given the most obvious adjacency heuristics, models can estimate signaling between adjacent cells, but more complex communication across larger spatial scales may be hard to detect effectively. Ideally, these models can look at signaling across all features, though computational complexity may require low-dimensional latent factor representations to tractably model complex signaling. Bayesian representations can provide proper uncertainty quantification and identify multiple parameter optima that explain the data equally well, but also require more expensive computation for posterior distributions.

Using the specific location of molecules, our second data representation allows for increased granularity and ability to look for causal signals. Here, models can explicitly condition on the location of a molecule inside or outside a cell as a proxy for determining its contribution to signaling behavior. Proteins near the membrane, for example, are more likely to be involved in some extracellular signaling than nuclear proteins. In these cases, the coordinate of a molecule might be considered rather than the cell center:

where $c_{n/-i}$ and $m_{n/-i}$ represent the coordinates and identities of molecules in cells other than i , and $\epsilon$ is white noise. Here, $f_1$ is dependent on the cell type, positing some shared spatial organization across cells of the same type. $f_2$ accounts for some variation from the organization of the other molecules in the cell and $f_3$ accounts for variation from molecules outside the cell. In this setup, $f_2$ captures intra-cellular signaling, perhaps of some cascading pathway, and $f_3$ captures inter-cellular signaling.

Like the models based on cell count tables, opportunities exist to model local and global effects at molecular resolution. Data with both intra-cellular and inter-cellular behavior measurements will be needed to calibrate the effectiveness of such a model, though the identification of known pathways serves as a model evaluation metric. Similar computational challenges in terms of dimension of possible gene-gene interactions will plague these kinds of models, which may require the development of latent variable models of single-cell spatial organization.

For both approaches, we are missing an important variable in the time dependency of signaling. A spatial measurement only provides a snapshot of the present; some molecules may be moving towards their destinations while others with important interaction effects may have just degraded. The current location may not be entirely informative about the relevant signaling actors. As multiple spatial snapshots and live-cell imaging become more affordable and widespread, models that explicitly include dynamic behaviors will be invaluable for establishing causality in biological signaling processes.

II. Methods to investigate the relationship between morphology and expression

When biologists study the relationship between morphology and expression, they require measurements of cell shape and molecular counts. These may come from paired histology and sequencing or a combination of cell segmentation and count measurements from in situ fluorescence. In addition to our count matrix X from earlier, let $\mathcal {S}$ containing $s_i \in {1, 2, \dots , N}$ cells represent the measurements of morphology, generally images or derived features. An experiment captures one realization of the distribution over morphology, cell position, and cell molecular state $p(\mathcal {S}, X, C).$

The analysis methods that currently exist that connect cell morphology and state make two strong assumptions: first, that observations from each cell are independent, and, second, that the position of the cell in space does not affect the morphology: $p(s_i, x_i | s_{-1}, x_{-1}, C) = p(s_i, x_i)$ . Then, one set of measurements is defined as a function of the other; shape as a function of gene expression, $s_i|x_i \sim f(x_i)$ , or gene expression as a function of shape, $x_i|s_i \sim f(s_i)$ . This is a reasonable assumption to make with current data and suggests a tractable class of model, but it obscures the complexity of the underlying mechanobiology that considers both intrinsic cell state and extrinsic environmental factors in cell morphology [ 133 ].

A natural opportunity in this space is to jointly model morphology and expression together, possibly by representing morphology using functional data analyses [ 134 ] or an autoencoder. Within a latent variable model, we may learn a shared representation of both cellular state and some encoding of cellular morphology Z given some form $s_i, x_i|z_i \sim f(z_i)$ . Canonical correlation analysis, for example, has been used to jointly learn embeddings of gene expression and histology images for bulk RNA-seq data [ 10 ]. Given sufficient single-cell data for network training, similar methods could be used to capture the relationship at single-cell resolution without causality assumptions.

More intriguing are models that are able to capture the effect of nearby cell morphology and expression, similar to the signaling models explored before. A simple model would decompose the likelihood of expression and morphology, $p(x_i, s_j| x_{-i}, s_{-i}, C)$ , into terms representing the intrinsic cell morphology and deviations induced by environmental effects. With appropriate data, one could imagine more sophisticated models that are able to account for the organization of cells alongside their shapes and expression, a full joint model of $p(X, \mathcal {S}, C).$ Models of this type will likely require multiple replicates, both technical and biological, of spatial experiments to accurately estimate these distributions. But the increased use of spatial experiments and expanded fields-of-view in each sample will open these avenues for investigation.

Returning to our second data representation—the list of molecular locations, identities, and cellular groupings—the opportunity exists to model the molecular level effects on morphology and, conversely, the change in spatial distribution of molecules given morphology. A simple model might rely on the assumption of independence between cells, and posit that $s_i|m_i, c_i \sim f(m_i, c_i).$ The correct functional form will depend on the representation of the shapes in $\mathcal {S}$ ; some tabular featurization can take advantage of regression models while a full image might require a neural network or other nonlinear model. Most exciting would be a model that can capture biophysical properties of the molecular interaction, learning how specific proteins or RNA molecules lead to the formation and warping of individual cell parts such as membrane structures within and across cells. Natural extensions would jointly consider cellular niches, to model $p(\mathcal {S}, M, O, C).$

For biologists who study dynamic processes such as development or cell response, time-dependent models will be the key to answering those scientific questions. The desired model will include the evolution of expression and morphology as a function of time, $p(\mathcal {S}, X, C | t)$ or $p(\mathcal {S}, M, O, C | t)$ . These models, coupled with appropriate data, may untangle the order in which morphology changes drive expression or expression changes morphology. Fitting models with clear biophysical structure—combined with hypothesis testing—may be one strategy to obtain interpretable and quantifiable results, e.g., estimating the mechanical forces contributed from membrane proteins on maintaining rigidity. Combining flexible machine learning methods with a biophysical interpretation will likely be required to fully capture the complexity of these dynamic morphological processes.

III. Methods to investigate how cellular environment shapes cellular state, cellular division, cell differentiation, and clonal dynamics

An exciting future direction is to map existing lineage-tracing methods onto spatial coordinates to better understand the spatial distribution and behavior of clones. Within our hypothetical framework, let us imagine that we have a count matrix X and spatial coordinates C , as well as some additional data structure Q that defines the relationship between cells (i.e., mother-daughter relationships in cells or cells that are part of one clonal population). One way to represent the ancestry of cells is by making Q an adjacency matrix that represents a directed tree, where $Q_{ij} = 1$ if cell i is a daughter of cell j . Connected components in this graph represent clonal outgrowth, and can be traced back to a single progenitor.

Although current analyses can identify clonal population sizes, it remains an open question whether these sizes are governed by cell-intrinsic or cell-extrinsic factors. If a set of cells Y represent a connected component of Q , we can identify generations at which clonal expansion slowed or halted, and ask whether clonal size (the cardinality of Y , | Y |) is a function of expression in surrounding cells, $|Y| = f_{1}(x_{-Y}, c_{-Y}) + f_{2}(x_{Y}),$ where $x_{Y}, x_{-Y}$ are the expression profiles of cells in Y and all cells not in Y , respectively. Similar to our spatial signaling framework, this treatment decouples the effects on clonal population size into clonal effects and the effects of environment around the clone.

Using this framework, we can also ask spatial questions about cells within a single clonal lineage: single-cell sequencing is able to resolve these populations but, before spatial sequencing, was unable to resolve their location. In some tissues, clones of cells remain close to each other in space and share a common niche. However, it is also possible for clones to split, migrate away from each other, and otherwise disperse in space. Given a set Y of clones originating from a single cell, we can study their dispersion patterns across space. Taking inspiration from our discussion of spatial signaling limits in cells, we can define a radius r and compute the probability of a given clone lying within radius r from other clones in the population, $p(\textrm{dist}(c_{i}, c_{j}) \le r | i, j \in Y).$

We can also ask whether this clonal colocalization is more, less, or equally likely if cells come from the same clone. This value can be calculated and tested for multiple clonal populations $q_{1}, q_{2}, \dots$ to identify clone-specific spatial distributions and behaviors of daughter cells to stay close to their mother or intentionally disperse. If there are members of a clonal lineage that are separated in space, we can then ask how this stratification may have occurred as a function of cell state as well as the local cell population: $\text {dist}(c_{i}, c_{j}) \le r | i, j \in Y\sim f(x_{i, j}, x_{-i, -j}, c).$

With sufficient spatial genomic data, learning the function f would most likely give higher weight to cells closer to the clones of interest, while also capturing environmental factors that define spatial clonal heterogeneity. The driving factors behind this spatial segregation may also be differentiation in the clones themselves; for instance, in the layers of the epidermis, cells from a single clone differentiate as they stratify from basal to apical [ 135 ]. In this case, spatial segregation may largely be a function of the intrinsic cell state within clones $x_{i, j}$ , and these effects, too, can be decoupled from effects from local cells.

IV. Methods to understand the relationship between cellular environment and rare events

A number of methods are needed to resolve the relationship between cellular environment and rare events. First, identification of rare events is essential but challenging given current pipelines. Currently, rare events are often filtered or overlooked in spatial transcriptomic data. Rare transcription events may not be captured without sufficient cells [ 136 ], and even when present may not be detected [ 137 ], often inseparable from poorly detected gene expression patterns [ 138 ]. For example, jackpot cells likely will not be identified because of the large numbers of zeros in marker transcripts of rare cell types across all cells, leading to marker genes being removed from the analysis and preventing identification of rare cell types. The opportunity here is to work with the mapped but unfiltered data to identify rare cell types through rare marker gene profiles.

Second, understanding the environmental characteristics that lead to rare events requires phenotyping a cellular environment and testing for enrichment of rare events within specific types of cellular environments. A number of methods perform related analyses, quantifying differential cell-type adjacency across a tissue [ 139 ], functional cellular collectives [ 140 , 141 , 142 ], and identifying de novo spatial domains [ 131 , 132 , 143 ].

Third, identifying enrichment of specific rare events within a cellular environment may be challenging given the paucity of these rare events and the complexity of a cellular environment. Outlier detection methods may be useful in this space, but these methods are broad; in the context of probabilistic models, identifying cells that have a low probability of being generated from a foundational model or latent space model of diverse cells may suggest a rare cell type or cell state [ 144 , 145 , 146 ]. A marked Poisson process may be useful to identify enrichment of specific environments in which these rare cell types arise. Marked Poisson processes consider specific events (here, a rare cell type) in the context of time or space with a “mark” or an identifier; then specific marks will filter up as enriched for rare events.

Concluding remarks

The rapid development of spatial genomics technologies, for the first time combining spatial imaging of cells and tissues with an analysis of their state and genomic profiles, provides an opportunity to revisit the types of questions we are able to ask and the quantitative methods we may use to answer those questions.

Here, we present four fundamental biological questions, each with profound implications for health and disease, that can now be addressed using spatial genomics technologies combined with appropriate machine learning methods. Future work will build on existing spatial genomics technologies and tailored analyses through the integration of time series data, better predictions of short-range and long-range correlations in multi-omic spatial datasets, and the ability to reason about biological processes across many scales.

Availability of data and materials

No new data and materials were produced for this paper. Referenced papers are available through their respective publishers.

Mazzarello P. A unifying concept: the history of cell theory. Nat Cell Biol. 1999;1(1):13–5.

Article Google Scholar

Fujiki Y, Hubbard AL, Fowler S, Lazarow PB. Isolation of intracellular membranes by means of sodium carbonate treatment: application to endoplasmic reticulum. J Cell Biol. 1982;93(1):97–102.

Article CAS PubMed Google Scholar

Ehrenreich J, Bergeron J, Siekevitz P, Palade G. Golgi fractions prepared from rat liver homogenates: I. isolation procedure and morphological characterization. J Cell Biol. 1973;59(1):45–72.

Article CAS PubMed PubMed Central Google Scholar

Koster AJ, Klumperman J. Electron microscopy in cell biology: integrating structure and function. Nat Rev Mol Cell Biol. 2003;4(9):6–9; SUPP.

Google Scholar

Hansma PK, Tersoff J. Scanning tunneling microscopy. J Appl Phys. 1987;61(2):1–24.

Alonso JL, Goldmann WH. Feeling the forces: atomic force microscopy in cell biology. Life Sci. 2003;72(23):2553–60.

Schermelleh L, Ferrand A, Huser T, Eggeling C, Sauer M, Biehlmaier O, Drummen GP. Super-resolution microscopy demystified. Nat Cell Biol. 2019;21(1):72–84.

McGettigan PA. Transcriptomics in the rna-seq era. Curr Opin Chem Biol. 2013;17(1):4–11.

Kulkarni A, Anderson AG, Merullo DP, Konopka G. Beyond bulk: a review of single cell transcriptomics methodologies and applications. Curr Opin Biotechnol. 2019;58:129–36.

Ash JT, Darnell G, Munro D, Engelhardt BE. Joint analysis of expression levels and histological images identifies genes associated with tissue morphology. Nat Commun. 2021;12(1):1609.

Schmauch B, Romagnoni A, Pronier E, Saillard C, Maillé P, Calderaro J, Kamoun A, Sefta M, Toldo S, Zaslavskiy M, et al. A deep learning model to predict RNA-Seq expression of tumours from whole slide images. Nat Commun. 2020;11(1):3877.

Comiter C, Vaishnav ED, Ciapmricotti M, Li B, Yang Y, Rodig SJ, Turner M, Pfaff KL, Jané-Valbuena J, Slyper M, et al. Inference of single cell profiles from histology stains with the single-cell omics from histology analysis framework (schaf). BioRxiv, 2023;2023–03.

Rios Velazquez E, Parmar C, Liu Y, Coroller TP, Cruz G, Stringfield O, Ye Z, Makrigiorgos M, Fennessy F, Mak RH, et al. Somatic mutations drive distinct imaging phenotypes in lung cancersomatic mutations and radiomic phenotypes. Can Res. 2017;77(14):3922–30.

Article CAS Google Scholar

Levsky JM, Singer RH. Fluorescence in situ hybridization: past, present and future. J Cell Sci. 2003;116(14):2833–8.

Bouwman BA, Crosetto N, Bienko M. The era of 3d and spatial genomics. Trends Genet 2022

Rodriques SG, Stickels RR, Goeva A, Martin CA, Murray E, Vanderburg CR, Welch J, Chen LM, Chen F, Macosko EZ. Slide-seq: a scalable technology for measuring genome-wide expression at high spatial resolution. Science. 2019;363(6434):1463–7.

Payne AC, Chiang ZD, Reginato PL, Mangiameli SM, Murray EM, Yao C-C, Markoulaki S, Earl AS, Labade AS, Jaenisch R, et al. In situ genome sequencing resolves dna sequence and structure in intact biological samples. Science. 2021;371(6532):3446.

Zhao T, Chiang ZD, Morriss JW, LaFave LM, Murray EM, Del Priore I, Meli K, Lareau CA, Nadaf NM, Li J, et al. Spatial genomics enables multi-modal study of clonal heterogeneity in tissues. Nature. 2022;601(7891):85–91.

Thul PJ, Åkesson L, Wiking M, Mahdessian D, Geladaki A, Ait Blal H, Alm T, Asplund A, Björk L, Breckels LM, et al. A subcellular map of the human proteome. Science. 2017;356(6340):3321.

Van Holde KE. Chromatin. Berlin: Springer Science & Business Media; 2012.

Martincorena I, Campbell PJ. Somatic mutation in cancer and normal cells. Science. 2015;349(6255):1483–9.

Goldberg AD, Allis CD, Bernstein E. Epigenetics: a landscape takes shape. Cell. 2007;128(4):635–8.

Jones PA, Takai D. The role of dna methylation in mammalian epigenetics. Science. 2001;293(5532):1068–70.

Das PM, Singal R. Dna methylation and cancer. J Clin Oncol. 2004;22(22):4632–42.

Meissner A, Gnirke A, Bell GW, Ramsahoye B, Lander ES, Jaenisch R. Reduced representation bisulfite sequencing for comparative high-resolution dna methylation analysis. Nucleic Acids Res. 2005;33(18):5868–77.

Buenrostro JD, Wu B, Chang HY, Greenleaf WJ. Atac-seq: a method for assaying chromatin accessibility genome-wide. Curr Protoc Mol Biol. 2015;109(1):21–9.

Article PubMed Central Google Scholar

Belmont AS. Nuclear compartments: an incomplete primer to nuclear compartments, bodies, and genome organization relative to nuclear architecture. Cold Spring Harb Perspect Biol. 2022;14(7): 041268.

Lieberman-Aiden E, Van Berkum NL, Williams L, Imakaev M, Ragoczy T, Telling A, Amit I, Lajoie BR, Sabo PJ, Dorschner MO, et al. Comprehensive mapping of long-range interactions reveals folding principles of the human genome. Science. 2009;326(5950):289–93.

Fortin J-P, Hansen KD. Reconstructing a/b compartments as revealed by hi-c using long-range correlations in epigenetic data. Genome Biol. 2015;16(1):1–23.

Jones MJ, Goodman SJ, Kobor MS. Dna methylation and healthy human aging. Aging Cell. 2015;14(6):924–32.

Zampieri M, Ciccarone F, Calabrese R, Franceschi C, Bürkle A, Caiafa P. Reconfiguration of dna methylation in aging. Mech Ageing Dev. 2015;151:60–70.

Arceo XG, Koslover EF, Zid BM, Brown A. Translation kinetics and diffusive timescales regulate mitochondrial localization of mrnas in yeast and mammalian cells. Biophys J. 2023;122(3):300.

Holt CE, Bullock SL. Subcellular mrna localization in animal cells and why it matters. Science. 2009;326(5957):1212–6.

Lécuyer E, Yoshida H, Parthasarathy N, Alm C, Babak T, Cerovina T, Hughes TR, Tomancak P, Krause HM. Global analysis of mrna localization reveals a prominent role in organizing cellular architecture and function. Cell. 2007;131(1):174–87.

Article PubMed Google Scholar

Little SC, Tkačik G, Kneeland TB, Wieschaus EF, Gregor T. The formation of the bicoid morphogen gradient requires protein movement from anteriorly localized mrna. PLoS Biol. 2011;9(3):1000596.

Laurent GS, Wahlestedt C, Kapranov P. The landscape of long noncoding rna classification. Trends Genet. 2015;31(5):239–51.

McKellar DW, Mantri M, Hinchman MM, Parker JS, Sethupathy P, Cosgrove BD, De Vlaminck I. Spatial mapping of the total transcriptome by in situ polyadenylation. Nat Biotechnol. 2023;41(4):513–20.

Mateescu B, Jones JC, Alexander RP, Alsop E, An JY, Asghari M, Boomgarden A, Bouchareychas L, Cayota A, Chang H-C, et al. Phase 2 of extracellular rna communication consortium charts next-generation approaches for extracellular rna research. Iscience. 2022;25(8)

Li J, Zhang Y, Yang C, Rong R. Discrepant mrna and protein expression in immune cells. Curr Genom. 2020;21(8):560–3.

Wang D. Discrepancy between mrna and protein abundance: insight from information retrieval process in computers. Comput Biol Chem. 2008;32(6):462–8.

Gry M, Rimini R, Strömberg S, Asplund A, Pontén F, Uhlén M, Nilsson P. Correlations between rna and protein expression profiles in 23 human cell lines. BMC Genom. 2009;10(1):1–14.

Liu Y, Beyer A, Aebersold R. On the dependency of cellular protein levels on mrna abundance. Cell. 2016;165(3):535–50.

Krishna RG, Wold F. Post-translational modifications of proteins. Methods in protein sequence analysis, 1993;167–172.

Gingras A-C, Abe KT, Raught B. Getting to know the neighborhood: using proximity-dependent biotinylation to characterize protein complexes and map organelles. Curr Opin Chem Biol. 2019;48:44–54.

Dunham WH, Mullin M, Gingras A-C. Affinity-purification coupled to mass spectrometry: Basic principles and strategies. Proteomics. 2012;12(10):1576–90.

Fries P. A mechanism for cognitive dynamics: neuronal communication through neuronal coherence. Trends Cogn Sci. 2005;9(10):474–80.

Shevach EM. Regulatory t cells in autoimmmunity. Annu Rev Immunol. 2000;18(1):423–49.

Woodcock EA, Matkovich SJ. Cardiomyocytes structure, function and associated pathologies. Int J Biochem Cell Biol. 2005;37(9):1746–51.

Domínguez Conde C, Xu C, Jarvis L, Rainbow D, Wells S, Gomes T, Howlett S, Suchanek O, Polanski K, King H, et al. Cross-tissue immune cell analysis reveals tissue-specific features in humans. Science. 2022;376(6594):5197.

Verhoeven BM, Mei S, Olsen TK, Gustafsson K, Valind A, Lindström A, Gisselsson D, Fard SS, Hagerling C, Kharchenko PV, et al. The immune cell atlas of human neuroblastoma. Cell Rep Med 3 (6)2022;

Raj A, Van Oudenaarden A. Nature, nurture, or chance: stochastic gene expression and its consequences. Cell. 2008;135(2):216–26.

Snijder B, Pelkmans L. Origins of regulated cell-to-cell variability. Nat Rev Mol Cell Biol. 2011;12(2):119–25.

Almet AA, Cang Z, Jin S, Nie Q. The landscape of cell-cell communication through single-cell transcriptomics. Curr Opin Syst Biol. 2021;26:12–23.

Nave K-A, Werner HB. Myelination of the nervous system: mechanisms and functions. Annu Rev Cell Dev Biol. 2014;30:503–33.

Baker NE. Emerging mechanisms of cell competition. Nat Rev Genet. 2020;21(11):683–97.

Liu S, Iorgulescu JB, Li S, Borji M, Barrera-Lopez IA, Shanmugam V, Lyu H, Morriss JW, Garcia ZN, Murray E, et al. Spatial maps of t cell receptors and transcriptomes reveal distinct immune niches and interactions in the adaptive immune response. Immunity. 2022;55(10):1940–52.

Marrahi AE, Lipreri F, Alber D, Hausser J. Four tumor micro-environmental niches explain a continuum of inter-patient variation in the macroscopic cellular composition of breast tumors. bioRxiv, 2022;2022–03.

Medaglia C, Giladi A, Stoler-Barak L, De Giovanni M, Salame TM, Biram A, David E, Li H, Iannacone M, Shulman Z, et al. Spatial reconstruction of immune niches by combining photoactivatable reporters and scrna-seq. Science. 2017;358(6370):1622–6.

Tikhonova AN, Lasry A, Austin R, Aifantis I. Cell-by-cell deconstruction of stem cell niches. Cell Stem Cell. 2020;27(1):19–34.

Mayer AT, Holman DR, Sood A, Tandon U, Bhate SS, Bodapati S, Barlow GL, Chang J, Black S, Crenshaw EC, et al. A tissue atlas of ulcerative colitis revealing evidence of sex-dependent differences in disease-driving inflammatory cell types and resistance to tnf inhibitor therapy. Sci Adv. 2023;9(3):1166.

Pelka K, Hofree M, Chen JH, Sarkizova S, Pirl JD, Jorgji V, Bejnood A, Dionne D, William HG, Xu KH, et al. Spatially organized multicellular immune hubs in human colorectal cancer. Cell. 2021;184(18):4734–52.

Lane SW, Williams DA, Watt FM. Modulating the stem cell niche for tissue regeneration. Nat Biotechnol. 2014;32(8):795–803.

Tepass U, Theres C, Knust E. crumbs encodes an egf-like protein expressed on apical membranes of drosophila epithelial cells and required for organization of epithelia. Cell. 1990;61(5):787–99.

Regev A, Teichmann S, Rozenblatt-Rosen O, Stubbington M, Ardlie K, Amit I, Arlotta P, Bader G, Benoist C, Biton M, et al. The human cell atlas white paper. arXiv preprint arXiv:1810.05192 2018;

Shahan R, Hsu C-W, Nolan TM, Cole BJ, Taylor IW, Greenstreet L, Zhang S, Afanassiev A, Vlot AHC, Schiebinger G, et al. A single-cell arabidopsis root atlas reveals developmental trajectories in wild-type and cell identity mutants. Dev Cell. 2022;57(4):543–60.

Sikkema L, Ramírez-Suástegui C, Strobl DC, Gillett TE, Zappia L, Madissoon E, Markov NS, Zaragosi L-E, Ji Y, Ansari M, et al. An integrated cell atlas of the lung in health and disease. Nat Med 2023;1–15.

Nguyen QH, Pervolarakis N, Blake K, Ma D, Davis RT, James N, Phung AT, Willey E, Kumar R, Jabart E, et al. Profiling human breast epithelial cells using single cell rna sequencing identifies cell diversity. Nat Commun. 2018;9(1):2028.

Article PubMed PubMed Central Google Scholar

Consortium TM, coordination Schaum Nicholas 1 Karkanias Jim 2 Neff Norma F. 2 May Andrew P. 2 Quake Stephen R. quake@ stanford. edu 2 3 f Wyss-Coray Tony twc@ stanford. edu 4 5 6 g Darmanis Spyros spyros. darmanis@ czbiohub. org 2 h, O., coordination Batson Joshua 2 Botvinnik Olga 2 Chen Michelle B. 3 Chen Steven 2 Green Foad 2 Jones Robert C. 3 Maynard Ashley 2 Penland Lolita 2 Pisco Angela Oliveira 2 Sit Rene V. 2 Stanley Geoffrey M. 3 Webber James T. 2 Zanini Fabio 3, L., data analysis Batson Joshua 2 Botvinnik Olga 2 Castro Paola 2 Croote Derek 3 Darmanis Spyros 2 DeRisi Joseph L. 2 27 Karkanias Jim 2 Pisco Angela Oliveira 2 Stanley Geoffrey M. 3 Webber James T. 2 Zanini Fabio 3, C.: Single-cell transcriptomics of 20 mouse organs creates a tabula muris. Nature 562(7727), 2018;367–372 .

Hung R-J, Hu Y, Kirchner R, Liu Y, Xu C, Comjean A, Tattikota SG, Li F, Song W, Ho Sui S, et al. A cell atlas of the adult drosophila midgut. Proc Natl Acad Sci. 2020;117(3):1514–23.

Cao J, Packer JS, Ramani V, Cusanovich DA, Huynh C, Daza R, Qiu X, Lee C, Furlan SN, Steemers FJ, Adey A, Waterston RH, Trapnell C, Shendure J. Comprehensive single-cell transcriptional profiling of a multicellular organism. Science. 2017;357(6352):661–7. https://doi.org/10.1126/science.aam8940.

Taylor DM, Aronow BJ, Tan K, Bernt K, Salomonis N, Greene CS, Frolova A, Henrickson SE, Wells A, Pei L, et al. The pediatric cell atlas: defining the growth phase of human development at single-cell resolution. Dev Cell. 2019;49(1):10–29.

Chen D, Wang W, Wu L, Liang L, Wang S, Cheng Y, Zhang T, Chai C, Luo Q, Sun C, et al. Single-cell atlas of peripheral blood mononuclear cells from pregnant women. Clin Transl Med. 2022;12(5):821.

Wilk AJ, Rustagi A, Zhao NQ, Roque J, Martínez-Colón GJ, McKechnie JL, Ivison GT, Ranganath T, Vergara R, Hollis T, et al. A single-cell atlas of the peripheral immune response in patients with severe covid-19. Nat Med. 2020;26(7):1070–6.

Schiller HB, Montoro DT, Simon LM, Rawlins EL, Meyer KB, Strunz M, Vieira Braga FA, Timens W, Koppelman GH, Budinger GS, et al. The human lung cell atlas: a high-resolution reference map of the human lung in health and disease. Am J Respir Cell Mol Biol. 2019;61(1):31–41.

Zhou Y, Xu J, Hou Y, Bekris L, Leverenz JB, Pieper AA, Cummings J, Cheng F. The alzheimer’s cell atlas (taca): A single-cell molecular map for translational therapeutics accelerator in alzheimer’s disease. Alzheimer’s & Dementia: Transl Res Clin Interve. 2022;8(1):12350.

Grubman A, Chew G, Ouyang JF, Sun G, Choo XY, McLean C, Simmons RK, Buckberry S, Vargas-Landin DB, Poppe D, et al. A single-cell atlas of entorhinal cortex from individuals with alzheimer’s disease reveals cell-type-specific gene expression regulation. Nat Neurosci. 2019;22(12):2087–97.

Winkler EA, Kim CN, Ross JM, Garcia JH, Gil E, Oh I, Chen LQ, Wu D, Catapano JS, Raygor K, et al. A single-cell atlas of the normal and malformed human brain vasculature. Science. 2022;375(6584):7377.

Starling E. Discussion on the therapeutic value of hormones. Proceedings of the Royal Society of Medicine 7(Ther_Pharmacol). 1914;29–31.

Nair A, Chauhan P, Saha B, Kubatzky KF. Conceptual evolution of cell signaling. Int J Mol Sci. 2019;20(13):3292.

Levi-Montalcini R, Hamburger V. Selective growth stimulating effects of mouse sarcoma on the sensory and sympathetic nervous system of the chick embryo. J Exp Zool. 1951;116(2):321–61.

Hokin MR, Hokin LE. Enzyme secretion and the incorporation of p32 into phospholipides of pancreas slices. J Biol Chem. 1953;203(2):967–77.

Krebs EG, Fischer EH. The phosphorylase b to a converting enzyme of rabbit skeletal muscle. Biochem Biophys Acta. 1956;20:150–7.

Aoki K, Kumagai Y, Sakurai A, Komatsu N, Fujita Y, Shionyu C, Matsuda M. Stochastic erk activation induced by noise and cell-to-cell propagation regulates cell density-dependent proliferation. Mol Cell. 2013;52(4):529–40.

McFann SE, Shvartsman SY, Toettcher JE. Putting in the erk: Growth factor signaling and mesoderm morphogenesis. Curr Top Dev Biol. 2022;149:263–310.

Marmion RA, Simpkins AG, Barrett LA, Denberg DW, Zusman S, Schottenfeld-Roames J, Schüpbach T, Shvartsman SY. Stochastic phenotypes in ras-dependent developmental diseases. Curr Biol. 2023;33(5):807–16.

Green JB, Sharpe J. Positional information and reaction-diffusion: two big ideas in developmental biology combine. Development. 2015;142(7):1203–11.

Merle M, Messio L, Mozziconacci J. Turing-like patterns in an asymmetric dynamic ising model. Phys Rev E. 2019;100(4): 042111.

Breakspear M, Heitmann S, Daffertshofer A. Generative models of cortical oscillations: neurobiological implications of the kuramoto model. Front Hum Neurosci. 2010;4:190.

Petkova MD, Tkačik G, Bialek W, Wieschaus EF, Gregor T. Optimal decoding of cellular identities in a genetic network. Cell. 2019;176(4):844–55.

Tkačik G, Callan CG Jr, Bialek W. Information flow and optimization in transcriptional regulation. Proc Natl Acad Sci. 2008;105(34):12265–70.

Eng C-HL, Lawson M, Zhu Q, Dries R, Koulena N, Takei Y, Yun J, Cronin C, Karp C, Yuan G-C, et al. Transcriptome-scale super-resolved imaging in tissues by rna seqfish+. Nature. 2019;568(7751):235–9.

Yuan Y, Bar-Joseph Z. Gcng: graph convolutional networks for inferring gene interaction from spatial transcriptomics data. Genome Biol. 2020;21(1):1–16.

Cang Z, Nie Q. Inferring spatial and signaling relationships between cells from single cell transcriptomic data. Nat Commun. 2020;11(1):2084.

Arnol D, Schapiro D, Bodenmiller B, Saez-Rodriguez J, Stegle O. Modeling cell-cell interactions from spatial molecular data with spatial variance component analysis. Cell Rep. 2019;29(1):202–11.

Fischer DS, Schaar AC, Theis FJ. Modeling intercellular communication in tissues using spatial graphs of cells. Nat Biotechnol 2022;1–5.

Vento-Tormo R, Efremova M, Botting RA, Turco MY, Vento-Tormo M, Meyer KB, Park J-E, Stephenson E, Polański K, Goncalves A, et al. Single-cell reconstruction of the early maternal-fetal interface in humans. Nature. 2018;563(7731):347–53.

Efremova M, Vento-Tormo M, Teichmann SA, Vento-Tormo R. Cellphonedb: inferring cell-cell communication from combined expression of multi-subunit ligand-receptor complexes. Nat Protoc. 2020;15(4):1484–506.

Garcia-Alonso L, Handfield L-F, Roberts K, Nikolakopoulou K, Fernando RC, Gardner L, Woodhams B, Arutyunyan A, Polanski K, Hoo R, et al. Mapping the temporal and spatial dynamics of the human endometrium in vivo and in vitro. Nat Genet. 2021;53(12):1698–711.

Verma A, Jena SG, Isakov DR, Aoki K, Toettcher JE, Engelhardt BE. A self-exciting point process to study multicellular spatial signaling patterns. Proc Natl Acad Sci. 2021;118(32):2026123118.

Borjini N, Paouri E, Tognatta R, Akassoglou K, Davalos D. Imaging the dynamic interactions between immune cells and the neurovascular interface in the spinal cord. Exp Neurol. 2019;322: 113046.

Nava MM, Miroshnikova YA, Biggs LC, Whitefield DB, Metge F, Boucas J, Vihinen H, Jokitalo E, Li X, Arcos JMG, et al. Heterochromatin-driven nuclear softening protects the genome against mechanical stress-induced damage. Cell. 2020;181(4):800–17.

GTEx Consortium: Genetic effects on gene expression across human tissues. Nature 550(7675);204–213.

Haghighi M, Caicedo JC, Cimini BA, Carpenter AE, Singh S. High-dimensional gene expression and morphology profiles of cells across 28,000 genetic and chemical perturbations. Nat Methods. 2022;1–8.

Stirling DR, Swain-Bowden MJ, Lucas AM, Carpenter AE, Cimini BA, Goodman A. Cell Profiler 4: improvements in speed, utility and usability. BMC Bioinf. 2021;22:1–11.

Ramezani M, Bauman J, Singh A, Weisbart E, Yong J, Lozada ME, Way GP, Kavari SL, Diaz C, Haghighi M, et al. A genome-wide atlas of human cell morphology. bioRxiv, 2023;2023–08.

Goodfellow I, Pouget-Abadie J, Mirza M, Xu B, Warde-Farley D, Ozair S, Courville A, Bengio Y. Generative adversarial networks. Commun ACM. 2020;63(11):139–44.

Lee H, Welch JD. Morphnet predicts cell morphology from single-cell gene expression. bioRxiv, 2022;2022–10.

Sivanandan S, Leitmann B, Lubeck E, Sultan MM, Stanitsas P, Ranu N, Ewer A, Mancuso JE, Phillips ZF, Kim A, et al. A pooled cell painting crispr screening platform enables de novo inference of gene function by self-supervised deep learning. bioRxiv, 2023;2023–08.

McSwiggen DT, Liu H, Tan R, Agramunt Puig S, Akella LB, Berman R, Bretan M, Chen H, Darzacq X, Ford K, et al. High-throughput single molecule tracking identifies drug interactions and cellular mechanisms. bioRxiv, 2023;2023–01.

Sun J, Ramos A, Chapman B, Johnnidis JB, Le L, Ho Y-J, Klein A, Hofmann O, Camargo FD. Clonal dynamics of native haematopoiesis. Nature. 2014;514(7522):322–7.

Fabre MA, de Almeida JG, Fiorillo E, Mitchell E, Damaskou A, Rak J, Orrù V, Marongiu M, Chapman MS, Vijayabaskar M, et al. The longitudinal dynamics and natural history of clonal haematopoiesis. Nature. 2022;606(7913):335–42.

Klein AM, Doupé DP, Jones PH, Simons BD. Kinetics of cell division in epidermal maintenance. Phys Rev E. 2007;76(2): 021910.

Klein AM, Doupé DP, Jones PH, Simons BD. Mechanism of murine epidermal maintenance: Cell division and the voter model. Phys Rev E. 2008;77(3): 031907.

Parigini C, Greulich P. Universality of clonal dynamics poses fundamental limits to identify stem cell self-renewal strategies. Elife. 2020;9:56532.

Gudmundsdottir H, Wells AD, Turka LA. Dynamics and requirements of t cell clonal expansion in vivo at the single-cell level: effector function is linked to proliferative capacity. J Immunol. 1999;162(9):5212–23.

Gerrits A, Dykstra B, Kalmykowa OJ, Klauke K, Verovskaya E, Broekhuis MJ, de Haan G, Bystrykh LV. Cellular barcoding tool for clonal analysis in the hematopoietic system. Blood, J Am Soc Hematol. 2010;115(13):2610–8.

CAS Google Scholar

Nguyen LV, Pellacani D, Lefort S, Kannan N, Osako T, Makarem M, Cox CL, Kennedy W, Beer P, Carles A, et al. Barcoding reveals complex clonal dynamics of de novo transformed human mammary cells. Nature. 2015;528(7581):267–71.

Spanjaard B, Hu B, Mitic N, Olivares-Chauvet P, Janjuha S, Ninov N, Junker JP. Simultaneous lineage tracing and cell-type identification using crispr-cas9-induced genetic scars. Nat Biotechnol. 2018;36(5):469–73.

Ishiguro S, Ishida K, Sakata RC, Mori H, Takana M, King S, Bashth O, Ichiraku M, Masuyama N, Takimoto R, et al.: A multi-kingdom genetic barcoding system for precise target clone isolation. BioRxiv, 2023;2023–01.

Koster MI, Roop DR. Mechanisms regulating epithelial stratification. Annu Rev Cell Dev Biol. 2007;23:93–113.

Colom B, Alcolea MP, Piedrafita G, Hall MW, Wabik A, Dentro SC, Fowler JC, Herms A, King C, Ong SH, et al. Spatial competition shapes the dynamic mutational landscape of normal esophageal epithelium. Nat Genet. 2020;52(6):604–14.

Colom B, Herms A, Hall M, Dentro S, King C, Sood R, Alcolea M, Piedrafita G, Fernandez-Antoran D, Ong S, et al. Mutant clones in normal epithelium outcompete and eliminate emerging tumours. Nature. 2021;598(7881):510–4.

Blanpain C, Fuchs E. Plasticity of epithelial stem cells in tissue regeneration. Science. 2014;344(6189):1242281.

Ma Y, Zhou X. Spatially informed cell-type deconvolution for spatial transcriptomics. Nat Biotechnol. 2022;40(9):1349–59.

Ru B, Huang J, Zhang Y, Aldape K, Jiang P. Estimation of cell lineages in tumors from spatial transcriptomics data. Nat Commun. 2023;14(1):568.

Elyanow R, Zeira R, Land M, Raphael BJ. Starch: copy number and clone inference from spatial transcriptomics data. Phys Biol. 2021;18(3): 035001.

Shaffer SM, Dunagin MC, Torborg SR, Torre EA, Emert B, Krepler C, Beqiri M, Sproesser K, Brafford PA, Xiao M, et al. Rare cell variability and drug-induced reprogramming as a mode of cancer drug resistance. Nature. 2017;546(7658):431–5.

Reiter JG, Makohon-Moore AP, Gerold JM, Heyde A, Attiyeh MA, Kohutek ZA, Tokheim CJ, Brown A, DeBlasio RM, Niyazov J, et al. Minimal functional driver gene heterogeneity among untreated metastases. Science. 2018;361(6406):1033–7.

Elowitz MB, Levine AJ, Siggia ED, Swain PS. Stochastic gene expression in a single cell. Science. 2002;297(5584):1183–6.

Swain PS, Elowitz MB, Siggia ED. Intrinsic and extrinsic contributions to stochasticity in gene expression. Proc Natl Acad Sci. 2002;99(20):12795–800.

Townes FW, Engelhardt BE. Nonnegative spatial factorization applied to spatial genomics. Nat Methods. 2023;20(2):229–38.

Velten B, Braunger JM, Argelaguet R, Arnol D, Wirbel J, Bredikhin D, Zeller G, Stegle O. Identifying temporal and spatial patterns of variation from multimodal data using MEFISTO. Nat Methods. 2022;19(2):179–86.

Yeung T, Georges PC, Flanagan LA, Marg B, Ortiz M, Funaki M, Zahir N, Ming W, Weaver V, Janmey PA. Effects of substrate stiffness on cell morphology, cytoskeletal structure, and adhesion. Cell Motil Cytoskelet. 2005;60(1):24–34.

Meng K, Wang J, Crawford L, Eloyan A. Randomness and statistical inference of shapes via the smooth Euler characteristic transform. arXiv preprint arXiv:2204.12699 2022;

Lechler T, Fuchs E. Asymmetric cell divisions promote stratification and differentiation of mammalian skin. Nature. 2005;437(7056):275–80.

Moffitt JR, Hao J, Wang G, Chen KH, Babcock HP, Zhuang X. High-throughput single-cell gene-expression profiling with multiplexed error-robust fluorescence in situ hybridization. Proc Natl Acad Sci. 2016;113(39):11046–51.

Groiss S, Pabst D, Faber C, Meier A, Bogdoll A, Unger C, Nilges B, Strauss S, Föderl-Höbenreich E, Hardt M, et al. Highly resolved spatial transcriptomics for detection of rare events in cells. bioRxiv, 2021;2021–10.

Torre E, Dueck H, Shaffer S, Gospocic J, Gupte R, Bonasio R, Kim J, Murray J, Raj A. Rare cell detection by single-cell rna sequencing as guided by single-molecule rna fish. Cell Syst. 2018;6(2):171–9.

Cable DM, Murray E, Shanmugam V, Zhang S, Zou LS, Diao M, Chen H, Macosko EZ, Irizarry RA, Chen F. Cell type-specific inference of differential expression in spatial transcriptomics. Nat Methods. 2022;19(9):1076–87.

Schürch CM, Bhate SS, Barlow GL, Phillips DJ, Noti L, Zlobec I, Chu P, Black S, Demeter J, McIlwain DR, et al. Coordinated cellular neighborhoods orchestrate antitumoral immunity at the colorectal cancer invasive front. Cell. 2020;182(5):1341–59.

Xu C, Jin X, Wei S, Wang P, Luo M, Xu Z, Yang W, Cai Y, Xiao L, Lin X, et al. Deepst: identifying spatial domains in spatial transcriptomics by deep learning. Nucleic Acids Res. 2022;50(22):131–131.

Shi X, Zhu J, Long Y, Liang C. Identifying spatial domains of spatially resolved transcriptomics via multi-view graph convolutional networks. Brief Bioi 2023;278.

Shang L, Zhou X. Spatially aware dimension reduction for spatial transcriptomics. Nat Commun. 2022;13(1):7203.

Theodoris CV, Xiao L, Chopra A, Chaffin MD, Al Sayed ZR, Hill MC, Mantineo H, Brydon EM, Zeng Z, Liu XS, et al. Transfer learning enables predictions in network biology. Nature. 2023;1–9.

Verma A, Engelhardt BE. A robust nonlinear low-dimensional manifold for single cell rna-seq data. BMC Bioinf. 2020;21(1):1–15.

Lopez R, Regier J, Cole MB, Jordan MI, Yosef N. Deep generative modeling for single-cell transcriptomics. Nat Methods. 2018;15(12):1053–8.

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Acknowledgements

The authors would like to acknowledge the incredible work of Tami Tolpa in creating the figures in this manuscript.

BEE and AV were funded by Helmsley Trust grant AWD1006624, NIH NCI 5U2CCA233195, CZI, and NIH NHGRI R01 HG012967. BEE is a CIFAR Fellow in the Multiscale Human Program.

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Siddhartha G. Jena and Archit Verma have contributed equally to this work.

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Department of Stem Cell and Regenerative Biology, Harvard, 7 Divinity Ave, Cambridge, MA, USA

Siddhartha G. Jena

Gladstone Institutes, 1650 Owens Street, San Francisco, CA, 94158, USA

Archit Verma

Stanford University, 1265 Welch Road, x327, Stanford, CA, 94305, USA

Barbara E. Engelhardt

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SGJ, AV, and BEE drafted, wrote, and edited this manuscript.

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Correspondence to Barbara E. Engelhardt .

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Jena, S.G., Verma, A. & Engelhardt, B.E. Answering open questions in biology using spatial genomics and structured methods. BMC Bioinformatics 25 , 291 (2024). https://doi.org/10.1186/s12859-024-05912-5

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Overcoming deterrents to modular construction in affordable housing: a systematic review.

1. Introduction

2. materials and methods, 2.1. research strategy, 2.2. data collection, 2.3. metadata extraction and data analysis, 3.1. categorisation of deterrents of mc in ah, 3.2. analysis of deterrents of mc in ah based on mean index score, 3.3. content and pareto analysis of deterrents of mc in ah, 3.3.1. environmental deterrents, 3.3.2. social and cultural deterrents, 3.3.3. technical and construction deterrents, 3.3.4. industry and market deterrents, 3.3.5. economic deterrents, 3.3.6. regulatory and policy deterrents, 3.3.7. administrative and bureaucratic deterrents, 3.4. tism modelling of the deterrents of mc in ah, 3.5. mitigating vital few deterrents of mc in ah, 4. discussion and implications, 4.1. discussions, 4.2. theoretical implications, 4.3. practical implications, 4.4. policy implications, 4.5. approach and results limitations, 5. conclusions, supplementary materials, author contributions, institutional review board statement, informed consent statement, data availability statement, conflicts of interest.

Serial Number	Title of the Paper	Type of Paper	Source	Source Country	Reference
1	Fostering Social Sustainability: Inclusive Communities through Prefabricated Housing	Journal	Buildings	Australia	[ ]
2	A Review of Prefabricated Housing Evolution, Challenges, and Prospects Towards Sustainable Development in Libya	Journal	International Journal of Sustainable Development and Planning	Libya	[ ]
3	Nudge or mandate: an exploration into the constraints of volumetric modular construction in Australia	Journal	Smart and Sustainable Built Environment	Australia	[ ]
4	Prefabrication and Modular Construction—A Potential Solution to Affordable and Temporary Housing in Ontario?	Conference	Lecture Notes in Civil Engineering	Canada	[ ]
5	Implementing modular integrated construction in high-rise high-density cities: perspectives in Hong Kong	Journal	Building Research and Information	Hong Kong	[ ]
6	Analysing value creation in social housing construction in remote communities—application to Nunavik (Canada)	Journal	Built Environment Project and Asset Management	Canada	[ ]
7	Motivations and market solutions for flexible housing in Finland	Journal	Journal of Housing and the Built Environment	Finland	[ ]
8	Delivering human-centred housing: understanding the role of post-occupancy evaluation and customer feedback in traditional and innovative social housebuilding in England	Journal	Construction Management and Economics	United Kingdom	[ ]
9	Assessment of Modular Construction System Made with Low Environmental Impact Construction Materials for Achieving Sustainable Housing Projects	Journal	Sustainability	Chile	[ ]
10	The Emerging Constraints in the Implementation of Prefabrication for Public Housing in the Philippines using Principal Component Analysis	Conference	International Conference on Construction in the 21st Century	Philippines	[ ]
11	Suitability of Modular Technology for House Construction in Sri Lanka: A Survey and a Case Study	Journal	Buildings	Sri Lanka	[ ]
12	Problems and challenges of the built environment and the potential of prefabricated architecture	Journal	Archives of Civil Engineering	Poland	[ ]
13	Research on Modularization of Prefabricated Affordable Housing in Zhengzhou Based on the Concept of Sustainable Development	Conference	Advances in Transdisciplinary Engineering	China	[ ]
14	Implementation of a novel data-driven approach to optimise UK offsite housing delivery	Conference	IOP Conference Series: Earth and Environmental Science	United Kingdom	[ ]
15	Affordable Housing with Prefabricated Construction Technology in India: An Approach to Sustainable Supply	Conference	ECS Transactions	India	[ ]
16	Analysis of challenges and opportunities of prefabricated sandwich panel system: A solution for affordable housing in India	Conference	Materials Today: Proceedings	India	[ ]
17	Embodied Energy Consumption in the Residential Sector: A Case Study of Affordable Housing	Journal	Sustainability	United Kingdom	[ ]
18	Prefab micro-units as a strategy for affordable housing	Journal	Housing Studies	United States	[ ]
19	Prefabricated Houses—A Model to Sustainable Housing Market	Conference	ECS Transactions	India	[ ]
20	Customization of on-site assembly services by integrating the internet of things and BIM technologies in modular integrated construction	Journal	Automation in Construction	Hong Kong	[ ]
21	Application of sustainable prefabricated wall technology for energy efficient social housing	Journal	Sustainability	India	[ ]
22	Systemized design to deliver leaner mid-rise timber housing	Conference	World Conference on Timber Engineering	Austria	[ ]
23	Potentials and Challenges of Accessory Dwelling Units Using Modular Construction	Conference	Computing in Civil Engineering	United States	[ ]
24	Analysis of skill shortages in prefabricated residential construction: A case for New Zealand	Conference	Proceedings of the 37th Annual ARCOM Conference	New Zealand	[ ]
25	Critical barriers to sustainability attainment in affordable housing: International construction professionals’ perspective	Journal	Journal of Cleaner Production	Hong Kong	[ ]
26	Modeling the Impact of Barriers on Sustainable Housing in Developing Countries	Journal	Journal of Urban Planning and Development	Hong Kong	[ ]
27	Critical success factors, barriers and challenges for adopting offsite prefabrication: A systematic literature review	Conference	ARCOM 2020—Association of Researchers in Construction Management	United Kingdom	[ ]
28	Customer-oriented approaches to housing affordability in industrialised house building	Conference	Joint Asia-Pacific Network for Housing Research and Australasian Housing Researchers Conference, APNHR and AHRC 2018	Australia	[ ]
29	Environmental cost-benefit analysis of prefabricated public housing in Beijing	Journal	Sustainability	China	[ ]
30	Integrated design experiences for energy-efficient housing in Chile	Journal	Construction Innovation	Chile	[ ]
31	Adoption of Prefabrication in Small Scale Construction Projects	Journal	Civil Engineering Journal (Iran)	Saudi Arabia	[ ]
32	Assembling an innovative social housing project in Melbourne: mapping the potential for social innovation	Journal	Housing Studies	Australia	[ ]
33	Awareness level and adoption of modular construction for affordable housing in Nigeria: Architects’ perspective	Journal	International Journal of Innovative Technology and Exploring Engineering	Nigeria	[ ]
34	An Internet of Things-enabled BIM platform for on-site assembly services in prefabricated construction	Journal	Automation in Construction	China	[ ]
35	D3 sustainable homes-an alternative design for high-rise affordable housing in tropical climates	Journal	Malaysian Construction Research Journal	Malaysia	[ ]
36	Research on the application of prefabricated buildings in affordable housing construction in China	Conference	Conference Proceedings of the 6th International Symposium on Project Management	China	[ ]
37	Energy and cost efficiency of a prefabricated timber social house in Chile: An interdisciplinary challenge	Conference	World Conference on Timber Engineering	Chile	[ ]
38	Major Barriers to Different Kinds of Prefabricated Public Housing in China: The Developers’ Perspective	Conference	Proceedings of the International Conference on Construction and Real Estate Management	China	[ ]
39	Comparison of Japanese and British off-site housing manufacturers and its relation with low/zero energy/carbon houses	Conference	Proceedings of 33rd PLEA International Conference: Design to Thrive	Japan	[ ]
40	Performance and Perception in Prefab Housing: An Exploratory Industry Survey on Sustainability and Affordability	Conference	Procedia Engineering	Australia	[ ]
41	Modelling process integration and its management—Case of a public housing delivery organization in United Arab Emirates	Conference	MATEC Web of Conferences	United Arab Emirates	[ ]
42	Space standardisation of low-income housing units in India	Journal	International Journal of Housing Markets and Analysis	India	[ ]
43	Affordable and sustainable housing—Architectural, urban strategies and analysing methodology	Conference	Central Europe Towards Sustainable Building 2016: Innovations for Sustainable Future	Germany	[ ]
44	Discrete-event simulation model for offsite manufacturing in Australia	Conference	Proceedings of the 31st Annual Association of Researchers in Construction Management Conference, ARCOM	Australia	[ ]
45	Technological and functional optimization of a modular construction system for flexible and adaptable multi-family housing	Journal	International Journal for Housing Science and Its Applications	Italy	[ ]
46	New Chilean building regulations and energy efficient housing in disaster zones: The thermal performance of prefabricated timber-frame dwellings	Conference	Proceedings—28th International PLEA Conference on Sustainable Architecture + Urban Design: Opportunities, Limits and Needs—Towards an Environmentally Responsible Architecture	Chile	[ ]

United Nations. UN Expert Urges Action to End Global Affordable Housing Crisis ; OHCHR: Geneva, Switzerland, 2023. [ Google Scholar ]
Forum, W.E. There’s a Global Housing Crisis. Here Are 4 Practical Solutions|World Economic Forum. Available online: https://www.weforum.org/agenda/2024/06/global-housing-crisis-practical-solutions/ (accessed on 2 July 2024).
Chan, A.P.C.C.; Adabre, M.A. Bridging the Gap between Sustainable Housing and Affordable Housing: The Required Critical Success Criteria (CSC). Build. Environ. 2019 , 151 , 112–125. [ Google Scholar ] [ CrossRef ]
Andersson, T.; Ribeirinho, M.J.; Blanco, J.L.; Mischke, J.; Rockhill, D.; Sjödin, E.; Strube, G.; Palter, R. The Next Normal in Construction ; Mckinsey Co.: New York, NY, USA, 2020. [ Google Scholar ]
United Nations. Affordable Housing Key for Development and Social Equality, UN Says on World Habitat Day ; United Nations Sustainable Development: Incheon, Republic of Korea, 2017. [ Google Scholar ]
Khan, A.; Yu, R.; Liu, T.; Guan, H.; Oh, E. Drivers towards Adopting Modular Integrated Construction for Affordable Sustainable Housing: A Total Interpretive Structural Modelling (TISM) Method. Buildings 2022 , 12 , 637. [ Google Scholar ] [ CrossRef ]
Bello, A.O.; Eje, D.O.; Idris, A.; Semiu, M.A.; Khan, A.A. Drivers for the Implementation of Modular Construction Systems in the AEC Industry of Developing Countries. J. Eng. Des. Technol. 2023 . ahead-of-print . [ Google Scholar ] [ CrossRef ]
Bertram, N.; Fuchs, S.; Mischke, J.; Palter, R.; Strube, G.; Woetzel, J. Modular Construction: From Projects to Products. Cap. Proj. Infrastruct. 2019 , 1 , 1–30. [ Google Scholar ]
Ahmad, K.A.; Rongrong, Y.; Ning, G.; Tingting, L.; James, W.; Samad, S.; Damien, C. Exploring Critical Risk Factors in Volumetric Modular Construction: Fault Tree Analysis with Stakeholders’ Perspectives on Probability and Impact. J. Arch. Eng. 2023 , 29 , 4023037. [ Google Scholar ] [ CrossRef ]
Bello, A.O.; Khan, A.A.; Idris, A.; Awwal, H.M. Barriers to Modular Construction Systems Implementation in Developing Countries’ Architecture, Engineering and Construction Industry. Eng. Constr. Arch. Manag. 2023 , 31 , 3148–3164. [ Google Scholar ] [ CrossRef ]
Abdul Nabi, M.; El-adaway, I.H. Modular Construction: Determining Decision-Making Factors and Future Research Needs. J. Manag. Eng. 2020 , 36 , 04020085. [ Google Scholar ] [ CrossRef ]
Maqbool, R.; Namaghi, J.R.; Rashid, Y.; Altuwaim, A. How Modern Methods of Construction Would Support to Meet the Sustainable Construction 2025 Targets, the Answer Is Still Unclear. Ain Shams Eng. J. 2023 , 14 , 101943. [ Google Scholar ] [ CrossRef ]
Khan, A.A.; Yu, R.; Liu, T.; Gu, N.; Walsh, J. Volumetric Modular Construction Risks: A Comprehensive Review and Digital-Technology-Coupled Circular Mitigation Strategies. Sustainability 2023 , 15 , 7019. [ Google Scholar ] [ CrossRef ]
Dolphin, M. Built Offsite. 2022. Available online: https://builtoffsite.com.au/emag/issue-15/ (accessed on 4 July 2024).
Feldmann, F.G.; Birkel, H.; Hartmann, E. Exploring Barriers towards Modular Construction—A Developer Perspective Using Fuzzy DEMATEL. J. Clean. Prod. 2022 , 367 , 133023. [ Google Scholar ] [ CrossRef ]
Ayinla, K.O.; Cheung, F.; Tawil, A.-R. Demystifying the Concept of Offsite Manufacturing Method. Constr. Innov. 2020 , 20 , 223–246. [ Google Scholar ] [ CrossRef ]
Esbieto, Z.R.; Magtibay, B.J.; Nangel, L.K.; Lindo, M.K. The Emerging Constraints in the Implementation of Prefabrication for Public Housing in the Philippines Using Principal Component Analysis. In Proceedings of the International Conference on Construction in the 21st Century, Amman, Jordan, 16–19 May 2023; Volume 2023-May. [ Google Scholar ]
McRobert, A. Customer-Oriented Approaches to Housing Affordability in Industrialised House Building. In Proceedings of the 2018 Joint Asia-Pacific Network for Housing Research and Australasian Housing Researchers Conference, APNHR and AHRC 2018—Proceedings, Gold Coast, Australia, 6–8 June 2018; pp. 67–77. [ Google Scholar ]
Anderson, N.; Wedawatta, G.; Rathnayake, I.; Domingo, N.; Azizi, Z. Embodied Energy Consumption in the Residential Sector: A Case Study of Affordable Housing. Sustainability 2022 , 14 , 5051. [ Google Scholar ] [ CrossRef ]
Navaratnam, S.; Satheeskumar, A.; Zhang, G.; Nguyen, K.; Venkatesan, S.; Poologanathan, K. The Challenges Confronting the Growth of Sustainable Prefabricated Building Construction in Australia: Construction Industry Views. J. Build. Eng. 2022 , 48 , 103935. [ Google Scholar ] [ CrossRef ]
Yu, R.; Gu, N.; Lee, G.; Khan, A. A Systematic Review of Architectural Design Collaboration in Immersive Virtual Environments. Designs 2022 , 6 , 93. [ Google Scholar ] [ CrossRef ]
Wuni, I.Y.; Shen, G.Q. Critical Success Factors for Modular Integrated Construction Projects: A Review. Build. Res. Inf. 2020 , 48 , 763. [ Google Scholar ] [ CrossRef ]
Moher, D.; Liberati, A.; Tetzlaff, J.; Altman, D.G. The PRISMA Group Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRIsMa Statement. PLoS Med. 2009 , 6 , e1000097. [ Google Scholar ] [ CrossRef ]
Khan, A.; Sepasgozar, S.; Liu, T.; Yu, R. Integration of Bim and Immersive Technologies for Aec: A Scientometric-swot Analysis and Critical Content Review. Buildings 2021 , 11 , 126. [ Google Scholar ] [ CrossRef ]
Mansoori, S. Which Is Better, a Conference Paper or Journal Publication? 2013. Available online: https://www.researchgate.net/post/Which_is_better_a_conference_paper_or_journal_publication (accessed on 4 July 2024).
Craft, R.C.; Leake, C. The Pareto Principle in Organizational Decision Making. Manag. Decis. 2002 , 40 , 729–733. [ Google Scholar ] [ CrossRef ]
Powell, T.; Sammut-Bonnici, T. Pareto Analysis. In Wiley Encyclopedia of Management ; John Wiley & Sons: Hoboken, NJ, USA, 2014; pp. 1–2. ISBN 9781118785317. [ Google Scholar ]
Wuni, I.Y. Mapping the Barriers to Circular Economy Adoption in the Construction Industry: A Systematic Review, Pareto Analysis, and Mitigation Strategy Map. Build. Environ. 2022 , 223 , 109453. [ Google Scholar ] [ CrossRef ]
Sushil Incorporating Polarity of Relationships in ISM and TISM for Theory Building in Information and Organization Management. Int. J. Inf. Manag. 2018 , 43 , 38–51. [ CrossRef ]
Sushil Interpreting the Interpretive Structural Model. Glob. J. Flex. Syst. Manag. 2012 , 13 , 87–106. [ CrossRef ]
Wuni, I.Y. A Systematic Review of the Critical Success Factors for Implementing Circular Economy in Construction Projects. Sustain. Dev. 2023 , 31 , 1195–1213. [ Google Scholar ] [ CrossRef ]
Wuni, I.Y.; Bao, Z.; Yevu, S.K.; Tetteh, M.O. Theorizing the Path Dependencies and Hierarchical Structure of the Multidimensional Risks in Green Building Projects. J. Build. Eng. 2023 , 68 , 106069. [ Google Scholar ] [ CrossRef ]
Wiegand, E.; Tapia, R.; Robertson, C. Urban Renovation and Densification: Economic and Technical Viability of Social Housing Based on Industrialized Prefabricated Timber Construction Systems. In Proceedings of the WCTE 2018—World Conference on Timber Engineering, Seoul, Republic of Korea, 20–23 August 2018. [ Google Scholar ]
Pan, W.; Yang, Y.; Pan, M. Implementing Modular Integrated Construction in High-Rise High-Density Cities: Perspectives in Hong Kong. Build. Res. Inf. 2023 , 51 , 354–368. [ Google Scholar ] [ CrossRef ]
Krippendorff, K. Content Analysis: An Introduction to Its Methodology ; Sage Publications: Thousand Oaks, CA, USA, 2018; ISBN 1506395678. [ Google Scholar ]
Nathers Rating Top Tips for Building for 7 Stars. 2022. Available online: https://www.nathers.gov.au/sites/default/files/2022-09/22726_Nathers_Newsletter.pdf (accessed on 4 July 2024).
Besser, D.; Rodrigues, L.; Bobadilla, A. New Chilean Building Regulations and Energy Efficient Housing in Disaster Zones: The Thermal Performance of Prefabricated Timber-Frame Dwellings. In Proceedings of the 28th International PLEA Conference on Sustainable Architecture + Urban Design: Opportunities, Limits and Needs—Towards an Environmentally Responsible Architecture, PLEA 2012, Lima, Perú, 7–9 November 2012. [ Google Scholar ]
Architecture, L.H.; Consulting, E.B. Site Planning and Design for Bushfire Light House Architecture and Science in Collaboration With Ember Bushfire Consulting ; Australian Institute of Architects: Melbourne, Australia, 2021; pp. 1–18. [ Google Scholar ]
GBCA Green Star Rating System|Green Building Council of Australia 2022. Available online: https://gbca-web.s3.amazonaws.com/media/documents/green-star-a-year-in-focus-final.pdf (accessed on 1 July 2024).
Tofiluk, A. Problems and Challenges of the Built Environment and the Potential of Prefabricated Architecture. Arch. Civ. Eng. 2023 , 69 , 405–424. [ Google Scholar ] [ CrossRef ]
Pawar, P.; Minde, P.; Kulkarni, M. Analysis of Challenges and Opportunities of Prefabricated Sandwich Panel System: A Solution for Affordable Housing in India. Mater. Today Proc. 2022 , 65 , 1946–1955. [ Google Scholar ] [ CrossRef ]
Shen, K.; Cheng, C.; Li, X.; Zhang, Z. Environmental Cost-Benefit Analysis of Prefabricated Public Housing in Beijing. Sustainability 2019 , 11 , 207. [ Google Scholar ] [ CrossRef ]
Hung, F.C.; Hamid, Z.A.; Beng, G.H.; Raymond, C.; Yin, C.C. D3 Sustainable Homes-an Alternative Design for High-Rise Affordable Housing in Tropical Climates. Malaysian Constr. Res. J. 2018 , 25 , 13–28. [ Google Scholar ]
Lucianto, A.E.; Herdiansyah, H. The Potential of Solar Panel Implementation Towards Sustainable Affordable Housing Development. In Proceedings of the 1st International Conference Earth Science and Energy, ICESE 2019, Kuala Lumpur, Malaysia, 7–8 November 2019; Institute of Physics Publishing, School of Environmental Science, Universitas Indonesia: Jakarta, Indonesia, 2020; Volume 519. [ Google Scholar ]
MacArthur, E. Universal Circular Economy Policy Goals ; Ellen MacArthur Foundation: Isle of Wight, UK, 2021. [ Google Scholar ]
Geographers Declare (A Climate Emergency)? 2021. Available online: https://www.tandfonline.com/doi/full/10.1080/00049182.2020.1866278 (accessed on 4 July 2024).
Riggs, W.; Sethi, M.; Meares, W.L.; Batstone, D. Prefab Micro-Units as a Strategy for Affordable Housing. Hous. Stud. 2022 , 37 , 742–768. [ Google Scholar ] [ CrossRef ]
Bakhaty, Y.; Kaluarachchi, Y. Critical Success Factors, Barriers and Challenges for Adopting Offsite Prefabrication: A Systematic Literature Review. In Proceedings of the ARCOM 2020—Association of Researchers in Construction Management, 36th Annual Conference 2020—Proceedings, Virtual, 7–8 September 2020; pp. 366–375. [ Google Scholar ]
Cheng, C.; Shen, K.; Li, X.; Zhang, Z. Major Barriers to Different Kinds of Prefabricated Public Housing in China: The Developers’ Perspective. In Proceedings of the ICCREM 2017: Prefabricated Buildings, Industrialized Construction, and Public-Private Partnerships—Proceedings of the International Conference on Construction and Real Estate Management 2017, Guangzhou, China, 10–12 November 2017; pp. 79–88. [ Google Scholar ]
Elsharie, W.; Shibani, A. Barriers to Growth of Small and Medium Enterprises (SMEs) in Libya. In Proceedings of the International Conference on Industrial Engineering and Operations Management, Singapore, 7–11 March 2021; p. 6414. [ Google Scholar ]
Lavikka, R.; Paiho, S. Motivations and Market Solutions for Flexible Housing in Finland. J. Hous. Built Environ. 2023 , 38 , 1789–1818. [ Google Scholar ] [ CrossRef ]
MacKenstadt, D.; Dang, H. Potentials and Challenges of Accessory Dwelling Units Using Modular Construction. In Proceedings of the Computing in Civil Engineering 2021—Selected Papers from the ASCE International Conference on Computing in Civil Engineering 2021, Orlando, FL, USA, 12–14 September 2021; pp. 1228–1235. [ Google Scholar ]
Khan, A.; Yu, R.; Liu, T. A Systematic Review of Risks in Modular Integrated Construction Practice. In Proceedings of the Conference: AUBEA 2021: Construction Education—Live the Future, Virtual, 27–29 October 2021. [ Google Scholar ]
Santana-Sosa, A.; Fadai, A.; Aichholzer, M.; Kamenik, M. Systemized Design to Deliver Leaner Mid-Rise Timber Housing. In Proceedings of the World Conference on Timber Engineering 2021, WCTE 2021, Santiago, Chile, 9–12 August 2021. [ Google Scholar ]
Zhou, J.X.; Shen, G.Q.; Yoon, S.H.; Jin, X. Customization of On-Site Assembly Services by Integrating the Internet of Things and BIM Technologies in Modular Integrated Construction. Autom. Constr. 2021 , 126 , 103663. [ Google Scholar ] [ CrossRef ]
Mostafa, S.; Chileshe, N. Discrete-Event Simulation Model for Offsite Manufacturing in Australia. In Proceedings of the 31st Annual Association of Researchers in Construction Management Conference, ARCOM 2015, Lincoln, UK, 7–9 September 2015; pp. 1043–1052. [ Google Scholar ]
Nagarjuna, G.; Arjun, B.S.; Shabarisha, N.; Gowri Shankar, R. Prefabricated Houses—A Model to Sustainable Housing Market. ECS Trans. 2022 , 107 , 3781–3792. [ Google Scholar ]
Roy, U.K.; Roy, M. Space Standardisation of Low-Income Housing Units in India. Int. J. Hous. Mark. Anal. 2016 , 9 , 88–107. [ Google Scholar ] [ CrossRef ]
Jain, S.; Bhandari, H. Affordable Housing with Prefabricated Construction Technology in India: An Approach to Sustainable Supply. ECS Trans. 2022 , 107 , 8513–8520. [ Google Scholar ] [ CrossRef ]
Suárez, J.L.; Gosselin, L.; Lehoux, N. Analysing Value Creation in Social Housing Construction in Remote Communities—Application to Nunavik (Canada). Built Environ. Proj. Asset Manag. 2023 , 13 , 493–508. [ Google Scholar ] [ CrossRef ]
Navaratnam, S.; Ngo, T.; Gunawardena, T.; Henderson, D. Performance Review of Prefabricated Building Systems and Future Research in Australia. Buildings 2019 , 9 , 38. [ Google Scholar ] [ CrossRef ]
Li, C.Z.; Xue, F.; Li, X.; Hong, J.; Shen, G.Q. An Internet of Things-Enabled BIM Platform for on-Site Assembly Services in Prefabricated Construction. Autom. Constr. 2018 , 89 , 146–161. [ Google Scholar ] [ CrossRef ]
Thai, H.T.; Ngo, T.; Uy, B. A Review on Modular Construction for High-Rise Buildings. Structures 2020 , 28 , 1265–1290. [ Google Scholar ] [ CrossRef ]
Wang, Z.L.; Shen, H.C.; Zuo, J. Risks in Prefabricated Buildings in China: Importance-Performance Analysis Approach. Sustainability 2019 , 11 , 3450. [ Google Scholar ] [ CrossRef ]
Shahzad, W.M.; Rajakannu, G.; Kordestani Ghalenoei, N. Potential of Modular Offsite Construction for Emergency Situations: A New Zealand Study. Buildings 2022 , 12 , 1970. [ Google Scholar ] [ CrossRef ]
Page, M.J.; McKenzie, J.E.; Bossuyt, P.M.; Boutron, I.; Hoffmann, T.C.; Mulrow, C.D.; Shamseer, L.; Grimshaw, J.M.; Hróbjartsson, A.; Lalu, M.M.; et al. The PRISMA 2020 statement: An updated guideline for reporting systematic reviews. BMJ 2021 , 372 , n71. [ Google Scholar ] [ CrossRef ]
Ziaesaeidi, P.; Noroozinejad Farsangi, E. Fostering Social Sustainability: Inclusive Communities through Prefabricated Housing. Buildings 2024 , 14 , 1750. [ Google Scholar ] [ CrossRef ]
Ammari, A.M.; Roosli, R. A Review of Prefabricated Housing Evolution, Challenges, and Prospects Towards Sustainable Development in Libya. Int. J. Sustain. Dev. Plan. 2024 , 19 , 1181–1194. [ Google Scholar ] [ CrossRef ]
Khan, A.A.; Yu, R.; Liu, T.; Gu, N.; Walsh, J.; Mohandes, S.R. Nudge or Mandate: An Exploration into the Constraints of Volumetric Modular Construction in Australia. Smart Sustain. Built Environ. 2024 . ahead-of-print . [ Google Scholar ] [ CrossRef ]
Roscetti, D.; Atkins, A.; Lacroix, D. Prefabrication and Modular Construction—A Potential Solution to Affordable and Temporary Housing in Ontario? In Proceedings of the Canadian Society of Civil Engineering Annual Conference 2022 ; Gupta, R., Sun, M., Brzev, S., Alam, M.S., Ng, K.T.W., Li, J., El Damatty, A., Lim, C., Eds.; Springer Nature: Cham, Switzerland, 2024; pp. 497–511. [ Google Scholar ]
Maslova, S.; Burgess, G. Delivering Human-Centred Housing: Understanding the Role of Post-Occupancy Evaluation and Customer Feedback in Traditional and Innovative Social Housebuilding in England. Constr. Manag. Econ. 2023 , 41 , 277–292. [ Google Scholar ] [ CrossRef ]
Romero Quidel, G.; Soto Acuña, M.J.; Rojas Herrera, C.J.; Rodríguez Neira, K.; Cárdenas-Ramírez, J.P. Assessment of Modular Construction System Made with Low Environmental Impact Construction Materials for Achieving Sustainable Housing Projects. Sustainability 2023 , 15 , 8386. [ Google Scholar ] [ CrossRef ]
Munmulla, T.; Hidallana-Gamage, H.D.; Navaratnam, S.; Ponnampalam, T.; Zhang, G.; Jayasinghe, T. Suitability of Modular Technology for House Construction in Sri Lanka: A Survey and a Case Study. Buildings 2023 , 13 , 2592. [ Google Scholar ] [ CrossRef ]
Liu, S.; Liu, Q.; Zhang, M. Research on Modularization of Prefabricated Affordable Housing in Zhengzhou Based on the Concept of Sustainable Development. Adv. Transdiscipl. Eng. 2022 , 23 , 1012–1023. [ Google Scholar ]
Ashayeri, I.; Goulding, J.; Heesom, D.; Arif, M.; Moore, N.; Obi, L.; Ahmed, N.; Saini, M. Implementation of a Novel Data-Driven Approach to Optimise UK Offsite Housing Delivery. In Proceedings of the IOP Conference Series: Earth and Environmental Science ; IOP Publishing: Bristol, UK, 2022; Volume 1101. [ Google Scholar ]
Chippagiri, R.; Gavali, H.R.; Ralegaonkar, R.V.; Riley, M.; Shaw, A.; Bras, A. Application of Sustainable Prefabricated Wall Technology for Energy Efficient Social Housing. Sustainability 2021 , 13 , 1195. [ Google Scholar ] [ CrossRef ]
Almughrabi, F.M.; Samarasinghe, D.A.S.; Rotimi, F.E. Analysis of Skill Shortages in Prefabricated Residential Construction: A Case for New Zealand. In Proceedings of the 37th Annual ARCOM Conference, ARCOM 2021, Virtual, 6–7 September 2021; pp. 481–490. [ Google Scholar ]
Adabre, M.A.; Chan, A.P.C.; Darko, A.; Osei-Kyei, R.; Abidoye, R.; Adjei-Kumi, T. Critical Barriers to Sustainability Attainment in Affordable Housing: International Construction Professionals’ Perspective. J. Clean. Prod. 2020 , 253 , 119995. [ Google Scholar ] [ CrossRef ]
Adabre, M.A.; Chan, A.P.C. Modeling the Impact of Barriers on Sustainable Housing in Developing Countries. J. Urban Plan. Dev. 2021 , 147 , 5020032. [ Google Scholar ] [ CrossRef ]
Echeverria-Valiente, E.; Garcia-Alvarado, R.; Celis-D’Amico, F.; Saelzer-Fuica, G. Integrated Design Experiences for Energy-Efficient Housing in Chile. Constr. Innov. 2019 , 19 , 236–255. [ Google Scholar ] [ CrossRef ]
Khahro, S.H.; Memon, N.A.; Ali, T.H.; Memon, Z.A. Adoption of Prefabrication in Small Scale Construction Projects. Civ. Eng. J. 2019 , 5 , 1099–1104. [ Google Scholar ] [ CrossRef ]
Raynor, K. Assembling an Innovative Social Housing Project in Melbourne: Mapping the Potential for Social Innovation. Hous. Stud. 2019 , 34 , 1263–1285. [ Google Scholar ] [ CrossRef ]
Sholanke, A.B.; Opoko, A.P.; Onakoya, A.O.; Adigun, T.F. Awareness Level and Adoption of Modular Construction for Affordable Housing in Nigeria: Architects’ Perspective. Int. J. Innov. Technol. Explor. Eng. 2019 , 8 , 251–257. [ Google Scholar ] [ CrossRef ]
Yang, Y.; Liu, Y. Research on the Application of Prefabricated Buildings in Affordable Housing Construction in China. In Proceedings of the 6th International Symposium on Project Management, ISPM 2018, Chongqing, China, 21–23 July 2018; pp. 93–101. [ Google Scholar ]
Baixas, J.I.; Ubilla, M.; Wiegand, E.; Victorero, F.; MacCawley, A.; Vera, J.; Avanzini, E.; Serra, E.; Luarte, M.; Cárcamo, S.; et al. Energy and Cost Efficiency of a Prefabricated Timber Social House in Chile: An Interdisciplinary Challenge. In Proceedings of the WCTE 2018—World Conference on Timber Engineering, Seoul, Republic of Korea, 20–23 August 2018. [ Google Scholar ]
Jimenez-Moreno, P.; Brennan, J. Comparison of Japanese and British Off-Site Housing Manufacturers and Its Relation with Low/Zero Energy/Carbon Houses. In Proceedings of the 33rd PLEA International Conference: Design to Thrive, PLEA 2017, Edinburgh, UK, 2–5 July 2017; Volume 1, pp. 1533–1540. [ Google Scholar ]
Dave, M.; Watson, B.; Prasad, D. Performance and Perception in Prefab Housing: An Exploratory Industry Survey on Sustainability and Affordability. Procedia Eng. 2017 , 180 , 676–686. [ Google Scholar ] [ CrossRef ]
Venkatachalam, S.; Diweiri, F.; Al Suwaidi, N. Modelling Process Integration and Its Management—Case of a Public Housing Delivery Organization in United Arab Emirates. In Proceedings of the MATEC Web of Conferences, Seoul, Republic of Korea, 22–25 August 2017; Volume 120. [ Google Scholar ]
Doemer, K.; Drexler, H.; Schultz-Granberg, J. Affordable and Sustainable Housing—Architectural, Urban Strategies and Analysing Methodology. In Proceedings of the CESB 2016—Central Europe Towards Sustainable Building 2016: Innovations for Sustainable Future, Prague, Czech Republic, 22–24 June 2016; pp. 716–723. [ Google Scholar ]
Ruta, M.; Sesana, M.M.; Sarti, F. Technological and Functional Optimization of a Modular Construction System for Flexible and Adaptable Multi-Family Housing. Int. J. Hous. Sci. Appl. 2013 , 37 , 43–52. [ Google Scholar ]

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Primary Keyword	Search Strategy
Modular construction	“modular construction” OR “modular integrated construction” OR “mic” OR “osc” OR “ppvc” OR “prefabrication” OR “prefabricated” OR “offsite construction” OR “offsite manufacturing” OR “osm” OR “offsite production” OR “modern method of construction” OR “industrialised construction” OR “industrialised building systems” OR “systems building” OR “prefabricated prefinished volumetric construction”
Affordable housing	“affordable housing” OR “low-income housing” OR “social housing” OR “public housing” OR “housing affordability” OR “sustainable housing” OR “community housing” OR “green affordable housing” OR “sustainable affordable housing” OR “energy-efficient housing” OR “eco-friendly housing”
Deterrents	deterrents OR barriers OR obstacles OR hurdles OR challenges OR impediments OR constraints OR limitations OR blockages OR roadblocks OR restrictions OR difficulties OR hindrances OR bottlenecks OR inhibitions OR inhibitors

ID	Deterrents	Total Frequency	Mean Index	Overall Rank
ED	Environmental deterrents	90	7.50	5
ED1	Strict waste disposal regulations and project timelines	8		31
ED2	Designing for resilience against natural disasters	11		10
ED3	Incorporation of renewable energy systems in design	4		62
ED4	Compliance with energy efficiency standards and costs	12		7
ED5	Limited availability of sustainable materials	9		23
ED6	Carbon footprint reduction strategies and feasibility	6		47
ED7	Environmental impact on local flora and fauna	4		62
ED8	Challenges in climate adaptation and resilience planning	6		47
ED9	High environmental impact assessments delaying projects	9		23
ED10	Biodiversity protection requirements impacting site selection	3		69
ED11	Environmental regulations affecting project feasibility	8		31
ED12	Stringent sustainability standards increasing costs	10		18
SCD	Social and Cultural deterrents	61	7.63	4
SCD1	Social equity concerns in housing distribution	6		47
SCD2	Lack of awareness and misinformation about modular benefits	9		23
SCD3	Resistance to change in construction methods	3		69
SCD4	Public scepticism about quality and durability	7		39
SCD5	Community resistance and stigma against modular housing	13		5
SCD6	Cultural biases and traditional housing perceptions	8		31
SCD7	Tenant acceptance and satisfaction challenges	4		62
SCD8	Cultural preferences and aesthetic concerns	11		10
TCD	Technical and Construction deterrents	77	7.00	7
TCD1	Challenges in achieving uniformity in construction	5		55
TCD2	Material compatibility issues and supply chain disruptions	4		62
TCD3	Construction delays during modular assembly	5		55
TCD4	Limited technical expertise and skills in modular construction	15		2
TCD5	Quality control issues and manufacturing standards	6		47
TCD6	Foundation problems and installation precision	3		69
TCD7	Safety concerns and regulatory compliance	8		31
TCD8	Integration challenges with existing infrastructure	6		47
TCD9	Site preparation complexities for modular projects	5		55
TCD10	Design limitations impacting architectural flexibility	11		10
TCD11	Logistics of transporting modular components	9		23
IMD	Industry and Market deterrents	71	7.89	3
IMD1	Skilled labour shortages and workforce challenges	10		18
IMD2	Lack of standardised practices and regulatory compliance	7		39
IMD3	Fragmentation and lack of collaboration in the industry	14		3
IMD4	Slow market acceptance and scalability of modular housing	11		10
IMD5	Perception of modular housing as lower quality	6		47
IMD6	Supply chain disruptions and logistical inefficiencies	5		55
IMD7	Resistance to innovation and traditional construction bias	9		23
IMD8	Reliability issues with modular suppliers and partners	5		55
IMD9	Competitive disadvantages compared to traditional methods	4		62
EcD	Economic deterrents	106	10.60	1
EcD1	Funding limitations and stakeholder financing	12		7
EcD2	Uncertainties in project cost estimates	7		39
EcD3	High initial investment costs and financing challenges	16		1
EcD4	Market conditions and affordability constraints	14		3
EcD5	Transportation expenses and logistics for modular units	7		39
EcD6	Rising construction material costs	8		31
EcD7	Return on investment concerns in modular construction	8		31
EcD8	Elevated insurance premiums for modular projects	11		10
EcD9	Economic feasibility and cost–benefit analysis	13		5
EcD10	High land costs and site acquisition challenges	10		18
RPD	Regulatory and Policy deterrents	72	8.00	2
RPD1	Political resistance and lobbying against modular construction	3		69
RPD2	Building code discrepancies and compliance issues	11		10
RPD3	Stringent zoning laws and land use restrictions	8		31
RPD4	Lack of supportive policies for modular housing	11		10
RPD5	Jurisdictional conflicts over regulatory oversight	4		62
RPD6	Uncertainty in regulatory requirements and interpretations	9		23
RPD7	Environmental regulations impacting project feasibility	7		39
RPD8	Compliance costs and financial implications	12		7
RPD9	Lengthy approval processes and bureaucratic delays	7		39
ABD	Administrative and Bureaucratic deterrents	100	7.14	6
ABD1	Challenges in stakeholder engagement and consultation	11		10
ABD2	Legal disputes and contractual issues	6		47
ABD3	Lengthy permit processes and regulatory hurdles	5		55
ABD4	High administrative costs impacting project budgets	9		23
ABD5	Policy inconsistencies across different jurisdictions	8		31
ABD6	Coordination challenges among multiple agencies	10		18
ABD7	Administrative delays in decision-making processes	7		39
ABD8	Lack of transparency in administrative procedures	7		39
ABD9	Lack of public sector support and funding	10		18
ABD10	Inefficient governance and project oversight	4		62
ABD11	Capacity constraints within regulatory bodies	9		23
ABD12	Bureaucratic red tape and project approval delays	6		47
ABD13	Documentation requirements and legal complexities	3		69
ABD14	Impact of political cycles and leadership changes	5		55

Category	Vital Few Deterrents	Strategies and Countermeasures	Relevant Actors and Stakeholders
Environmental	Compliance with energy efficiency standards and costs	Incentivise adoption through subsidies and grants	Government agencies, environmental organisations, financial institutions
	Designing for resilience against natural disasters	Develop standardised resilient designs	Architects, engineers, urban planners, disaster management agencies
	Stringent sustainability standards increasing costs	Streamline sustainability standards for cost-effectiveness	Standards organisations, policymakers, construction firms
	Limited availability of sustainable materials	Promote research and development of sustainable materials	Research institutions, construction firms, material suppliers
	High environmental impact assessments delaying projects	Streamline environmental assessment processes	Environmental agencies, regulatory bodies, project developers
	Strict waste disposal regulations and project timelines	Implement efficient waste management systems	Waste management companies, construction firms, regulatory bodies
	Environmental regulations affecting project feasibility	Adapt project plans to meet environmental regulations	Environmental consultants, regulatory bodies, project managers
Social and Cultural	Community resistance and stigma against modular housing	Engage communities through awareness programs and showcasing benefits	Community leaders, local governments, NGOs, media
	Cultural preferences and aesthetic concerns	Incorporate local cultural aesthetics in modular designs	Architects, cultural consultants, local communities
	Lack of awareness and misinformation about modular benefits	Launch educational campaigns to inform the public about modular benefits	Media, educational institutions, government agencies
	Cultural biases and traditional housing perceptions	Address cultural biases through targeted communication	Cultural consultants, community leaders, government agencies
Technical and Construction	Limited technical expertise and skills in modular construction	Invest in training programs and certifications for modular construction skills	Educational institutions, vocational training centres, industry associations
	Design limitations impacting architectural flexibility	Enhance design flexibility through modular innovations	Architects, designers, construction firms
	Logistics of transporting modular components	Optimise logistics planning and transportation routes	Logistics companies, transport agencies, construction firms
	Safety concerns and regulatory compliance	Strengthen safety protocols and ensure compliance with regulations	Safety inspectors, construction firms, regulatory bodies
	Integration challenges with existing infrastructure	Develop strategies for seamless integration with existing infrastructure	Infrastructure planners, construction firms, government agencies
	Quality control issues and manufacturing standards	Establish strict quality control measures and standards	Manufacturing firms, quality assurance teams, regulatory bodies
	Construction delays during modular assembly	Improve assembly processes and provide contingency planning	Project managers, construction teams, suppliers
Industry and Market	Skilled labour shortages and workforce challenges	Initiate training programs and improve working conditions	Educational institutions, labour unions, construction firms
	Fragmentation and lack of collaboration in the industry	Promote industry-wide collaboration and standardisation	Industry associations, construction firms, regulatory bodies
	Slow market acceptance and scalability of modular housing	Market modular benefits through campaigns and pilot projects	Marketing firms, construction companies, government agencies
	Resistance to innovation and traditional construction bias	Encourage innovation and provide incentives for adopting new technologies	Innovation hubs, industry associations, government agencies
	Lack of standardised practices and regulatory compliance	Develop industry-wide standards and enforce regulatory compliance	Standards organisations, regulatory bodies, industry associations
Administrative and Bureaucratic	Challenges in stakeholder engagement and consultation	Facilitate early stakeholder engagement and continuous communication	Project managers, community leaders, government agencies
	Lack of public sector support and funding	Provide targeted funding and incentives for modular projects	Government agencies, financial institutions, policymakers
	Coordination challenges among multiple agencies	Establish centralised coordination bodies or frameworks	Government agencies, regulatory bodies, project coordinators
	High administrative costs impacting project budgets	Streamline administrative processes to reduce costs	Administrative bodies, project managers, financial auditors
	Capacity constraints within regulatory bodies	Increase staffing and resources within regulatory agencies	Government agencies, regulatory bodies, policymakers
	Policy inconsistencies across different jurisdictions	Harmonise policies across regions to avoid inconsistencies	Policymakers, regulatory bodies, legal experts
	Administrative delays in decision-making processes	Implement time-bound decision-making processes	Government agencies, project managers, legal teams
	Lack of transparency in administrative procedures	Improve transparency and accountability in administrative procedures	Regulatory bodies, project stakeholders
	Bureaucratic red tape and project approval delays	Simplify approval processes and reduce bureaucratic hurdles	Government agencies, regulatory bodies, project coordinators
Economic	High initial investment costs and financing challenges	Offer low-interest loans and financial incentives	Financial institutions, government agencies, private investors
	Market conditions and affordability constraints	Implement policies to stabilise market conditions	Policymakers, economic planners, housing authorities
	Economic feasibility and cost–benefit analysis	Conduct thorough cost–benefit analyses and feasibility studies	Economic analysts, construction firms, government agencies
	Funding limitations and stakeholder financing	Explore alternative financing options and partnerships	Financial institutions, private investors, government agencies
	Elevated insurance premiums for modular projects	Negotiate insurance premiums and provide risk mitigation strategies	Insurance companies, construction firms, risk management experts
	High land costs and site acquisition challenges	Implement land acquisition strategies and provide subsidies	Land authorities, government agencies, developers
Regulatory and Policy	Building code discrepancies and compliance issues	Harmonise building codes across regions	Regulatory bodies, policymakers, construction firms
	Lack of supportive policies for modular housing	Develop and implement supportive modular housing policies	Government agencies, policymakers, industry associations
	Compliance costs and financial implications	Reduce compliance costs through streamlined processes	Regulatory bodies, construction firms, policymakers
	Uncertainty in regulatory requirements and interpretations	Clarify and standardise regulatory requirements	Regulatory bodies, legal experts, construction firms
	Stringent zoning laws and land use restrictions	Advocate for flexible zoning laws and land use policies	Urban planners, policymakers, developers

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Khan, A.A.; Amirkhani, M.; Martek, I. Overcoming Deterrents to Modular Construction in Affordable Housing: A Systematic Review. Sustainability 2024 , 16 , 7611. https://doi.org/10.3390/su16177611

Khan AA, Amirkhani M, Martek I. Overcoming Deterrents to Modular Construction in Affordable Housing: A Systematic Review. Sustainability . 2024; 16(17):7611. https://doi.org/10.3390/su16177611

Khan, Ayaz Ahmad, Mehdi Amirkhani, and Igor Martek. 2024. "Overcoming Deterrents to Modular Construction in Affordable Housing: A Systematic Review" Sustainability 16, no. 17: 7611. https://doi.org/10.3390/su16177611

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Review Article
Open access
Published: 03 September 2024

Achievements, challenges, and future prospects for industrialization of perovskite solar cells

Chuang Yang 1 na1 ,
Wenjing Hu 1 na1 ,
Jiale Liu 1 ,
Chuanzhou Han 1 ,
Qiaojiao Gao 1 ,
Anyi Mei 1 ,
Yinhua Zhou 1 ,
Fengwan Guo 2 &
Hongwei Han 1

Light: Science & Applications volume 13 , Article number: 227 ( 2024 ) Cite this article

Metrics details

Photonic devices
Solar energy and photovoltaic technology

In just over a decade, certified single-junction perovskite solar cells (PSCs) boast an impressive power conversion efficiency (PCE) of 26.1%. Such outstanding performance makes it highly viable for further development. Here, we have meticulously outlined challenges that arose during the industrialization of PSCs and proposed their corresponding solutions based on extensive research. We discussed the main challenges in this field including technological limitations, multi-scenario applications, sustainable development, etc. Mature photovoltaic solutions provide the perovskite community with invaluable insights for overcoming the challenges of industrialization. In the upcoming stages of PSCs advancement, it has become evident that addressing the challenges concerning long-term stability and sustainability is paramount. In this manner, we can facilitate a more effective integration of PSCs into our daily lives.

Degradation pathways in perovskite solar cells and how to meet international standards

Long-term operating stability in perovskite photovoltaics

Scalable fabrication and coating methods for perovskite solar cells and solar modules

Introduction.

Solar power has consistently emerged as one of the most promising, reliable, and renewable energy sources among various alternatives 1 , 2 . Since the discovery of the photovoltaic (PV) effect, solar cell technology has continued to evolve and advance, enabling the widespread adoption of solar power as a viable renewable resource 3 . Currently, silicon solar cells occupy a dominant position in the solar cell industry 4 . As alternative solar technologies, such as thin-film solar cells or perovskite solar cells (PSCs), continue to evolve, silicon solar cells are increasingly encountering competitive pressures in the market. These cutting-edge technologies hold the promise of delivering significant cost advantages and enhanced performance, sparking intense ongoing research efforts.

Metal halide perovskite materials have garnered significant interest as highly promising materials for photovoltaic devices due to their exceptional photoelectric properties 5 , 6 . These materials have captivated researchers and industry alike, as they offer great potential for advancing the field of photovoltaics. Following the initial fabrication of PSCs and their achievement with a power conversion efficiency (PCE) of 3.8%, research on PSCs has gained tremendous momentum 7 . With the persistent efforts of scientists, certified single-junction PSCs now boast a soul-stirring PCE of 26.1% (~0.0513 cm 2 ), which ushered in the dawn of the industrial development of PSCs 8 . As shown in Fig. 1 , in order to enhance the industrial feasibility of PSCs, it is imperative to undertake a thorough investigation of their complete life cycle. The intricate journey begins with sourcing raw materials, where the composition of perovskite plays a crucial role in adjusting the bandgap and enhancing stability. Subsequently, the meticulous creation of small-area PSCs hinges on achieving a high-quality perovskite film and establishing precise energy level alignment between the perovskite absorption layer and the charge transport layer. Advancing along this path toward the industrialization of PSCs entails the necessary transition to Perovskite Solar Modules (PSMs). During this phase, the primary objective is to minimize efficiency losses resulting from device amplification, where a variety of amplification techniques have been explored. Moving forward, researchers’ focus expands to exploring the versatile deployment of PSCs across various applications and scenarios. This represents our ultimate goal in harnessing the potential of these solar technologies. Last but certainly not least, we must extend our considerations to a critical aspect—sustainability. As PSCs fulfill their primary function, it becomes imperative to thoughtfully contemplate recycling mechanisms and embrace sustainable practices. This holistic understanding and management of the entire life cycle are pivotal in unlocking the full industrial potential inherent in PSCs, making it not just an energy solution but also an environmentally responsible technology.

However, compared to established PV technology and market demand, issues of PSCs about long-term stability, such as degradation and performance fluctuations, persist as challenges that should be overcome 9 . Moreover, the industrial application of PSCs still faces challenges related to scale, cost, and sustainable development in the life cycle 10 , 11 , 12 . These issues have emerged as significant constraints, demanding careful consideration and innovative solutions.

The collective objective revolves around the development of efficient, stable, cost-effective, large-scale, and sustainable PSCs. In this review, we delve into the primary challenges associated with the industrialization of PSCs, encompassing technological limitations, application constraints, and sustainable development. For the technological limitations, although only a small difference exists between PSCs and silicon solar cells in terms of device efficiency, there is a big gap in long-term stability. In addition, reducing the efficiency sacrifice brought by the device amplification process is also urgent to be addressed. Within the realm of application constraints, the crucial step toward enabling the diverse applications of PSCs across various scenarios lies in extending the device’s lifespan and optimizing its production cost so that it can maximize economic advantages. Ultimately, the reduction of pollution generated during PSC preparation remains paramount for fostering sustainable development.

Technology limitations

PSCs have gained prominence as the focus of research in the solar energy sector. Nevertheless, numerous challenges still persist, encompassing the need for continued efficiency enhancement, bolstered stability, and the establishment of scalable PSC production methods. Within this chapter, we will comprehensively address these concerns, expounding on each one and providing an overview of current remedial approaches.

The PCE and improvement strategies

The general structural formula of 3D organic-inorganic hybrid perovskite is ABX 3 , where A-site ion in perovskite compounds comprises methylamine ion (MA + ), formamidine ion (FA + ), or alkali metal ion, while the B-site ion consists of Pb 2+ or Sn 2+ , and X-site ions represent halogen ions. The structural diversity and huge composition space of perovskite make it possible to achieve a series of functional properties. Up to now, the highest PCE of single-junction PSCs reached 26.1%, which is comparable to that of monocrystalline silicon solar cells. However, opportunities for further improvement remain on the path towards achieving the Shockley-Queisser (S-Q) limit 13 . Based on the existing research, fine-tuning the optical bandgap of perovskite materials through composition engineering involving multicomponent A- and X-site ions offers a direct means of customizing the inherent characteristics of perovskite. This approach holds the potential to yield efficient and high-performance PSCs 14 . Besides, augmenting the PCE primarily encompasses the enhancement of crystal quality, the passivation of defects, the facilitation of charge extraction at interfaces, and other related measures.

The enhancement of crystal quality

Elevating the crystalline quality of perovskite films holds significant potential for enhancing the overall performance of PSCs. The LaMer model provides valuable insights into the nucleation and grain growth process of crystal participated from precursor solution 15 , 16 . Based on this theory, when the solvent’s evaporation rate is slow, the solution concentration gradually approaches the critical level over an extended period. This results in a low concentration of nuclei, allowing initial nuclei ample time and space to grow into larger crystals. While this fosters perovskite films with minimal grain boundaries, film coverage may be inadequate during this phase. Conversely, a high solvent evaporation rate swiftly elevates the solution concentration above the critical level. In this scenario, the concentration of atomic nuclei is high, limiting the time and space for their growth. This high concentration facilitates the formation of a uniform and fine perovskite film, albeit with an increased presence of grain boundaries 17 . Therefore, precise control of the solvent evaporation rate is crucial for achieving perovskite films with optimal uniformity, coverage, and roughness.

From the reported literature we can see that the formation of immediate phase can effectively decelerate the crystallization process, facilitating the growth of crystals with large size. The induction of the immediate phase can be realized either through solvents with high coordination ability or through the incorporation of additives 18 , 19 , 20 .

Lead iodide (PbI 2 ) is the precursor material of perovskite, which could be functioned as a Lewis acid. Solvents such as dimethyl sulfoxide (DMSO), thiourea, and pyridine furnish lone pairs of electrons, which can be classified as Lewis base. The interaction between these solvents and PbI 2 can give rise to Lewis acid-base interaction, as shown in Fig. 2a 21 . For instance, N,N-dimethylformamide (DMF) serves as a frequently used solvent in perovskite precursor solutions, which was applied to examine the effect of DMSO on the growth of perovskite films. Although the DMF molecular can be coordinated with PbI 2 , perovskite films produced through the conventional one-step method displayed needle-like morphology, leaving the substrate incompletely covered. This can be attributed to the comparatively lower coordination ability of DMF in comparison to DMSO, which impeded DMF from effectively postponing the MAI-PbI 2 reaction. The introduction of equimolar DMSO to DMF can lead to the formation of an intermediate phase, MAI-PbI 2 -DMSO, which effectively mitigates the rapid self-assembly crystallization stemming from the direct MAI-PbI 2 reaction. Following the volatilization of DMSO, a highly uniform MAPbI 3 film is meticulously generated (Fig. 2b ) 22 . The inclusion of DMSO can indeed facilitate immediate phase formation and prolong the crystallization process. However, it should be known that an increase in the content of DMSO may not necessarily lead to improved outcomes. Through strategic adjustments in the PbI 2 /DMSO ratio, a sequence of transformative phases within the immediate phase film can be observed as the content of DMSO increases. The transition occurred from a state of pure perovskite phase to a composite blend of perovskite/MA 2 Pb 3 I 8 (DMSO) 2 , progressing further to the distinct phase of pure MA 2 Pb 3 I 8 (DMSO) 2 , and ultimately to the combined MA 2 Pb 3 I 8 (DMSO) 2 /perovskite configuration (Fig. 2c ). Notably, these diverse intermediate phases exhibited varying relative perovskite crystal structures and qualities. The intermediate phase of pure MA 2 Pb 3 I 8 (DMSO) 2 exhibited a marked tendency for growth along the (110) direction. This growth behavior prompted the formation of perovskite film with reduced horizontal grain boundaries and decreased density of trap states. Consequently, this unique morphology translated into the highest PCE when evaluated within parallel group experiments. However, excessively slow crystallization rates resulting from high concentrations of DMSO led to irregular perovskite grain sizes and heightened surface roughness in the perovskite film 23 . Hence, solvent coordination ability should reside within an appropriate range so that it can achieve the optimal perovskite film with high crystallinity. Furthermore, the crystallization process can be influenced by factors such as solvent polarity, vapor pressure, boiling point, steric hindrance, and viscosity. Consequently, when choosing a solvent to regulate crystallization, it is essential to carefully consider how various solvent properties impact the crystallization process.

a Schematic diagram of Lewis acid-base interaction between solvent or additive and PbI 2 . Reproduced with permission from ref. 21 Copyright 2019 Wiley-VCH. b Perovskite films prepared by one-step method and their SEM images. Reproduced with permission from ref. 22 Copyright 2016 American Chemical Society. c Schematic diagram of the relationship between the content of DMSO and the composition of the intermediate phase. Reproduced with permission from ref. 23 Copyright 2017 Elsevier Ltd. d Photographs of DMA x (FA 0.83 Cs 0.17 ) 1–x Pb(Br 0.2 I 0.8 ) 3 Cl x perovskite films treated by different amounts of DMACl and their corresponding crystal structure. Reproduced with permission from ref. 24 Copyright 2022 Springer Nature. e The effective charge-carrier mobilities of perovskite films prepared by precursor solution with different concentrations of colloids. Reproduced with permission from ref. 26 Copyright 2017 Wiley-VCH. f Crystal structure simulation and SEM images under different processing methods. Reproduced with permission from ref. 30 Copyright 2018 American Chemical Society

Beyond solvents, the incorporation of additives can also foster the development of the immediate phase. Dimethylammonium was utilized to control the intermediate phases in the perovskite precursor through a high-temperature processing technique, in the absence of DMSO (Fig. 2d ). This method enabled precise control over the crystallization sequence, bringing about finely tuning in grain size, orientation, and overall crystallinity of the perovskite film, which resulted in fewer structural defects and higher PCE 24 .

The colloidal characteristics of the perovskite precursor solutions were observed to exhibit a direct correlation with both the defect concentration and crystallinity of the resulting perovskite film 25 . Hence, the interplay between an acidic additive and the dissolution of the colloidal framework has been established. Via facilitating the gradual dissolution of these colloids covering defined time regions, the nucleation, growth dynamics, and eventual morphology of perovskite film can be significantly modified. This enhancement in material quality fosters the reduction of microstrain and a remarkable increase in charge-carrier mobilities (Fig. 2e ). Employing precursor solution with a meticulously optimal colloidal concentration can yield outstanding optoelectronic performance of PSCs 26 .

Additionally, some other methods are also applied to gain highly crystallized perovskite film, for instance, anti-solvent engineering (ASE), gas-assisted preparation, gas-blowing fabrication, or some other methods 27 , 28 , 29 . As shown in Fig. 2f , by synergizing the one-step ASE approach with subsequent gas blowing, the MAPbI 3 film with high orientation and polycrystalline nanograins (150 ∼ 500 nm) can be effectively fabricated in the beginning. After being treated with anti-solvent-containing H 2 O, the perovskite grains were expanded to 1.5 μm. As a result, the PSCs reached an excellent PCE of 21% with a prominent fill factor (FF) of 86% 30 .

The passivation of defects

The reduced efficiencies compared to the theoretical counterparts can be attributed to discrepancies between the actual measured open circuit voltage ( V OC ) and FF. The decrement in V OC and FF is linked to losses stemming from Shockley-Read-Hall (SRH) recombination, a consequence of volume and interface defects 31 . Hence, the passivation of defects holds paramount significance in minimizing recombination and enhancing the photovoltaic performance of devices.

Perovskite crystals own low defect-formation energy in thermodynamics 32 . For example, perovskite crystals harbor a substantial quantity of dangling bonds on surfaces, notably uncoordinated ions like Pb 2+ or X − . These ions have the potential to act as defects in perovskite film 33 . The majority of defects reside within the shallow energy levels near the band edges, exhibiting electrical activity 34 . Conversely, anti-site and interstitial defects are positioned at deeper electronic levels, functioning as nonradiative recombination centers detrimental to device efficiency 35 .

Among the array of available methods, additive engineering has emerged as a remarkably efficient strategy for defect passivation. Generally speaking, the most potent approach for defect passivation involves leveraging Lewis acid-base interactions to passivate uncoordinated ions. The integration of Lewis acid and base additives into perovskite precursors can effectively reduce non-radiative recombination centers and defects at grain boundaries 36 , 37 , 38 .

Lewis acid encompasses specific ions or even molecules that can function as electron pair acceptors, which can effectively mitigate undercoordinated I − ions and Pb-I anti-site defects. Frequently employed Lewis acid additive mainly consists of cationic additives, fluorine-containing aromatic molecules, as well as fullerene and its derivatives 39 , 40 , 41 .

As for the cationic additive, given the valence distribution within the perovskite lattice and the redox stability of alkali metals, alkali metal cations with a positive charge are deemed optimal candidates for doping 42 . The incorporation of alkali metal cations (K + and Na + ) was proved to be an effective additive, leading to a significant enhancement in perovskite film quality with reduced grain boundaries and fewer trap states. This improvement resulted in an elevated built-in potential, ultimately resulting in higher PCE 43 . Besides, the incorporation of Rb + dopants has been substantiated as an effective strategy for diminishing nonradiative recombination via chemical passivation and eradicating hysteresis in PSCs 44 . The δ-FAPbI 3 can be suppressed by incorporating a mere 1% RbI into the precursor solution, employed for fabricating (FAPbI 3 ) 0.83 (MAPbBr 3 ) 0.17 perovskite film (Fig. 3a ). Impressively, samples containing Rb + exhibited prolonged charge carrier lifetimes exceeding 1 μs, along with heightened V OC and minimal current–voltage (J–V) hysteresis 45 .

a Photographs of perovskite film with different addition of RbI (0, 1, 5, 10%) at room temperature. Reproduced with permission from ref. 45 Copyright Royal Society of Chemistry. b Schematic view of the halogen bond interaction between the IPFB and a generic halogen anion. Reproduced with permission from ref. 41 Copyright 2014 American Chemical Society. c Molecular structure of TFPN and its passivation diagram. Reproduced with permission from ref. 47 Copyright 2021 American Chemical Society. d UV absorption spectra of the hybrid solution show the interaction between PCBM and perovksite ions. The inset image shows the interaction between I − and PCBM and the formation of PCBM radical anion and PCBM–halide radical. Reproduced with permission from ref. 49 Copyright 2015 Springer Nature. e The pKa value and PCE for different additives. f Schematic illustration of chemical reaction at perovskite surface with ANCl. Reproduced with permission from ref. 54 Copyright 2021 American Chemical Society. g Action mechanism diagram of additive dipole effect by DLBA, BLCA, and BLC on perovskite film. Reproduced with permission from ref. 57 Copyright 2023 Wiley-VCH. h Photographs of the unpassivated and passivated perovskite films before and after high humidity aging. i Passivation mechanism of perovskite treated by 2-MP. Reproduced with permission from ref. 58 Copyright 2019 Wiley-VCH

Lewis acid of the fluorine-containing aromatic variety exhibits potent electronegativity due to the presence of fluorine atoms. These atoms adeptly induce the withdrawal of electron density from both the adjacent aromatic ring and the distal end, resulting in the development of a positive charge on this particular side (Fig. 3b ). This unique interaction can effectively passivate defects through a non-covalent bonding effect 38 , 46 . For example, iodopentafluorobenzene (IPFB), wherein five fluorine atoms are strategically affixed to the five vertices of the benzene ring, was incorporated to coat the perovskite crystals. Fluorine engendered a reduction in electron density around the connected iodine atom within IPFB. This phenomenon led to a partial positive charge on the iodine, enabling it to establish a halogen bond with adjacent halogen atoms. Through this mechanism, uncoordinated halogen anti-site defects were effectively passivated 41 . Similarly, the tetrafluorophthalonitrile (TFPN) with four fluorine atoms was designed, which can interact with uncoordinated Pb 2+ , resulting in a proficient reduction of defect state density on the perovskite surface (Fig. 3c ). Besides, cyanogroup within TFPN effectively ameliorates defects from uncoordinated Pb 2+ . Moreover, with the incorporation of TFPN at the interface, the Fermi level of the perovskite absorbent layer experienced a discernible shift of approximately 0.15 eV towards its valence band, prompting the creation of a positive dipole oriented towards the perovskite. Consequently, an amplified electric field effect ensued at the interface, considerably heightening the efficiency of hole extraction and transportation 47 .

Fullerene derivatives can also passivate defects, inhibit non-recombination, and improve film quality 48 . For example, Xu et al. found that the PCBM can passivate the iodide-rich trap sites on the surface when incorporated at or near perovskite grain boundaries, which can reduce hysteresis and promote electron extraction 49 (Fig. 3d ).

Lewis base refers to ions or molecules that act as electron pair donors, rendering it adept at passivating electron-deficient defects, such as uncoordinated Pb 2+ . The prevalent passivation groups utilized as Lewis base primarily encompass those functional groups comprising N-, O-, or S-atoms 50 , 51 , 52 .

N-donor Lewis base molecules effectively mitigate the presence of ionic charged defects, such as Pb 2+ and I − , situated at grain boundaries or interfaces. This passivation is predominantly achieved through hydrogen bonding. In addition, amino-containing molecules with a certain steric hindrance can also anchor with perovskite to form low-dimensional perovskite, which can enhance the humidity stability of perovskite film. Tao et al. employed the new Lewis base additive, ethylenediamine chlorides (EDACl 2 ). This compound proved instrumental in facilitating the generation of perovskite films with fewer trap states. Relative photoelectric assessments unveiled that the inclusion of EDACl 2 enhanced the charge transport in the perovskite film, concurrently diminishing non-radiative recombination processes 53 . While N-donor molecules could effectively passivate uncoordinated Pb 2+ ions in perovskite, it is noteworthy that the protonic characteristics of the passivating agent may also exert adverse effects on perovskite film. Park et al. presented a comprehensive analysis of the impact of acid dissociation constants (K a ) in passivation agents on the photovoltaic performance of PSCs. A notable enhancement in PCE is observed when post-treated by cyclohexylammonium chloride (CYCl), the pKa value of which is 10.6. Conversely, the PCE experienced a decrease when treated with anilinium chloride (ANCl) with a relatively lower pKa value (4.6), primarily due to the unfavorable generation of increased traps induced by ANCl (Fig. 3e ). This discrepancy in PCE was ascribed to the degree of deprotonation (pK a ), which took a pivotal part in the formation of defect-mediated traps. The deprotonation process associated with lower-pK a ANCl led to the release of free iodide (Fig. 3f ), subsequently contributing to the emergence of iodide defects 54 . What’s more, the deprotonating effect of a highly basic Lewis base can lead to the deprotonation of the MA + cations in MAPbI 3 perovskite. This deprotonation process could potentially trigger the release of volatile organic molecules (FA and MA), consequently inducing lattice distortion or, in more severe cases, complete collapse of their crystal structures. The structural alteration ultimately contributed to the deterioration of the device’s performance 55 . Hence, when crafting N-donor Lewis base molecules, a judicious design approach must take account of the substantial implications of passivation and proton behavior to PSC devices.

Lewis base molecules with O-donor groups, such as carboxyl, exhibit a passivation effect akin to that of N-donor molecules. Iyer et al. introduced three additives, namely benzene carboxylic acid (BCA), benzene-1,3-dicarboxylic acid (BDCA), and benzene-1,3,5-tricarboxylic acid (BTCA), into the precursor solution. The incorporation of carboxylic acid moieties proved valid in modulating perovskite films, resulting in fewer trap states as well as ion migration. The presence of these additives during perovskite film formation exerted a profound effect on charge transfer dynamics, leading to enhanced performance and stability of the PSCs. Notably, devices incorporating BTCA exhibited the most remarkable outcomes, achieving the V OC up to 1.076 V, marking an increase of about 80 mV 56 . While carbonyl molecules have demonstrated their efficacy as additives for facilitating the preparation of PSCs with high performance, the relationship between the structure and property of carbonyl agents and their capacity to passivate defects in perovskite films remains unclear. Hence, Pang et al. selected a variety of carbonyl additives featuring a single carbonyl group and a robust π-conjugate structure, which included Biphenyl-4-carboxaldehyde (BLCA), 4-Acetyl-biphenyl (BLC), and 4-(N, N-Diphenylamino)-benzaldehyde (DLBA). This selection aimed to investigate the intricate interaction between the functional groups of these additives and perovskite film. Their investigation revealed a positive correlation between the molecular dipole of the additives and their interaction with uncoordinated Pb 2+ defects (Fig. 3g ). A more pronounced molecular dipole was conducive to an enhanced passivation effect of the carbonyl additives. Among these organic molecules, DLBA exhibited the highest polarity, underscoring exceptional proficiency in passivating defects in perovskite film 57 . Therefore, it is necessary to take into account the effect on molecular polarity (charge density of functional groups) in perovskite films when designing O-donor molecules. However, whether higher polarity can achieve a better passivation effect and if there is a critical value still needs to be further investigated.

S-donor molecules act in a similar way to N- or O-donor molecules. Zhu et al. introduced a bidentate molecule, 2-mercaptopyridine (2-MP), to enhance anchoring ability, thereby simultaneously diminishing defects and elevating stability. In comparison to monodentate molecules like pyridine (PY) and p-toluenethiol (PTT), MAPbI 3 film passivated by 2-MP exhibited a remarkable increase in photoluminescence (PL) lifetime and excellent thermal stability. What’s more, the unpassivated MAPbI 3 experienced a rapid transition from a black film to a transparent state within a 30-min timeframe, while the humid stability exhibited a marginal enhancement for PY and PTT-passivated MAPbI 3 , where a few persistent black dots were observed after 1 h. Notably, MAPbI 3 films passivated with 2-MP displayed unexpected resistance in a highly humid environment, showcasing minimal color alteration even after enduring concentrated moisture invasion for 5 h (Fig. 3h ). This may be owing to the robust bonding affinity of the 2-MP molecule with Pb 2+ ions through its bidentate anchoring, which prevents moisture from effectively competing and disrupting the connection between the passivating molecules and the perovskite surface. Consequently, the reactivity between ambient water molecules and the perovskite film is effectively suppressed, leading to a significantly enhanced energy barrier for the hydration reaction pathway (Fig. 3i ). These enhancements translated to a boosted PCE of 20.28%, with an inspiring V OC of 1.18 V, while the PCE of the control device is 18.35% 58 .

In general, this intricate interplay of Lewis acid and base additives holds the potential for enhanced PSC performance through defect passivation. Nonetheless, gaining a comprehensive grasp of the intricate mechanisms underlying complete passivation remains a formidable task, primarily due to the multifunctional nature of certain Lewis acids/bases. The integration of systematic theoretical simulation and experimental verification is essential to achieve effective passivation in various perovskite fabrication processes.

The facilitation of charge extraction

Enhanced charge extraction can be achieved through meticulously optimized energy level alignment, typically established at the interface between the electron transport layer (ETL)/perovskite or hole transport layer (HTL)/perovskite. Through the incorporation of an interfacial layer or the meticulous adjustment of either ETL or HTL band alignment, electron/hole transfer and extraction can be improved and V OC can be enhanced as well. The band offsets between the ETL and perovskite, as well as between the HTL and perovskite, play a pivotal role in governing carrier recombination at the relative interfaces. In practical terms as Fig. 4a, b , achieving a band offset of approximately 0.2 eV becomes imperative to facilitate effective charge extraction at the ETL/perovskite and HTL/perovskite interfaces 59 , 60 . The energy level disparities between neighboring layers can be fine-tuned by means of interface engineering 61 .

Energy level diagram of perovskites and charge transporting layer for a n–i–p and b p–i–n architecture PSCs. Reproduced with permission from ref. 293 Copyright 2018 Wiley-VCH. c The self-assembled monolayers between the SnO 2 and perovskite film. (BA is benzoic acid, PA is 4-pyridine carboxylic acid, CBA is 4-cyanobenzoic acid, ABA is 4-aminobenzoic acid, and C3 is 3-propanoic acid). d The work function and corresponding PCE for perovskite after being treated by different self-assembled monolayers. Reproduced with permission from ref. 63 Copyright 2017 American Chemical Society. e Chemical structures and electrostatic potential mapping images of the three molecules. f Schematic diagram of the effect of coulomb force regulation and their surface dipole direction by different functional groups. g Schematic energy-level diagrams of control, −OCH 3 , aniline, and −NO 2 molecule-treated CsPbBr 3 films. Reproduced with permission from ref. 64 Copyright 2021 American Chemical Society. h The band alignment diagram. i J–V curves for PSCs treated with different molecules. Reproduced with permission from ref. 65 Copyright 2020 American Chemical Society

Perovskite/ETL interface

Enhancing electron extraction and injection represents a crucial avenue for augmenting the efficiency of PSCs. These pivotal processes transpire at the interface of the ETL and the perovskite layer. Hence, the property of this interface wields significant influence over the whole device’s performance.

Rubidium bromide (RbBr) was employed to deposit onto the SnO 2 surface. The introduction of RbBr was found to exert a transformative effect, resulting in the narrowing of SnO 2 ’s bandgap from 3.58 to 3.34 eV. This modification led to a reduction in the energy barrier at the ETL/perovskite interface, thereby enhancing electronic contact between the two components. This pivotal alteration significantly contributed to the pronounced enhancement in overall device performance 62 .

Nonetheless, Yang et al. have introduced diverse functional groups onto the surface of SnO 2 to establish a range of chemical interactions with the perovskite layer (Fig. 4c ). Surprisingly, the performance of the perovskite solar cell devices deviates from the expected trend dictated by energy level alignment theory. This phenomenon underscored the pivotal role of chemical interactions as the predominant determinant of interfacial optoelectronic properties (Fig. 4d ). Notably, the utilization of a self-assembled monolayer (SAM) composed of 4-pyridinecarboxylic acid yields the highest PCE, highlighting the profound impact of tailored chemical interactions on enhancing device performance 63 .

Therefore, in the process of choosing molecules for interface modification, it is imperative to consider not only the alteration in work function but also the ramifications of interfacial chemical interactions.

Perovskite/HTL interface

The role of HTL encompasses both electron blocking and hole transport functions. A crucial step within PSCs is the extraction of holes, which takes place at the interface between the HTL and the perovskite layer. Achieving highly efficient hole extraction at the HTL/perovskite interface holds significant potential for enhancing device performance.

Tang et al. explored the utilization of a series of self-assembled aniline molecules to modify the surface of CsPbBr 3 films. By altering the functional groups at para-position which exhibited varying electronegativities such as electron-withdrawing −NO 2 and electron-donating −OCH 3 , remarkable enhancements in photovoltaic parameters are observed (Fig. 4e ). As depicted in Fig. 4f , the introduction of –OCH 3 led to the greatest electron accumulation within the benzene ring, in contrast to –NO 2 and pristine aniline. The discrepancy arose due to the charge transfer initiated by the disparity in electronegativities. This phenomenon enhanced the electrostatic force, thereby facilitating both hole transfer and hole extraction from the perovskite to the carbon electrode. Based on the analysis of ultraviolet photoelectron spectroscopy (UPS), the work functions for the control, −OCH 3 -, aniline-, and −NO 2 -sample are established as −3.86 eV, −3.92 eV, −4.00 eV, and −4.13 eV, respectively (Fig. 4g ). Integrating insights from the UPS spectra depicting the valence band evolution, alongside the unaltered bandgap of 2.35 eV, the energy level diagram of CsPbBr 3 PSCs post-treatment unveiled a perceptible transformation manifesting as a surface shift towards less n-type behavior in CsPbBr 3 and an elevated energy level. Notably, this elevation proved advantageous for both hole extraction and the redirection of photogenerated electrons away from the interface. Particularly, a − OCH 3 -tailored all-inorganic CsPbBr 3 solar cell achieved a PCE of 9.81%, accompanied by a remarkably improved V OC of 1.632 V 64 .

Li et al. investigated the effect of N-((4-(N,N,N-triphenyl)phenyl)ethyl)ammonium bromide (TPA-PEABr) in the PSCs. This molecular, together with triphenylamine (TPA) and N -(2-( N , N , N -triphenyl)ethyl)ammonium bromide (TPA-EABr), was strategically introduced as an interface buffer layer via spin-coating onto the perovskite surface. The investigation unveiled that the highest occupied molecular orbital (HOMO) energy level of these TPA derivatives falls within the range of approximately −5.4 to −5.5 eV (Fig. 4h ). Significantly, this energy level positioning places it between the perovskite layer and the HTL, effectively bridging the energy gap and contributing to an enhanced alignment of energy levels between these components. In contrast to the control devices, the PCE of PSCs treated by TPA remained nearly unchanged. However, an enhancement in PCE was observed from 16.69% to 17.40% when treated by TPA-EABr, and ultimately reaching an impressive 18.15% for the devices treated by TPA-PEABr. The enhanced performance stems from the surface passivation provided by TPA-PEABr, coupled with the refined alignment of energy levels achieved upon the incorporation of TPA-PEABr as the buffer layer 65 .

Tandem solar cells

Increasing the PCE of solar cells to its theoretical limit is the key to minimizing energy losses and improving cost-effectiveness. While the current PCE of single junction devices is not up to expectations, tandem solar cells with a wide bandgap absorber and a low bandgap absorber can maximize light utilization, resulting in a more desirable PCE. The perovskite with adjustable bandgap can be combined in tandem cells with both wide and low bandgap materials, such as perovskite/organic, perovskite/perovskite, perovskite/Si, perovskite/CIGS. Excitingly, the certified efficiency of perovskite/Si tandem cells has surpassed 33.7%, which is above the theoretical Shockley-Queisser limit (33%) 66 . However, the theoretical efficiency of the perovskite/Si tandem cell is much higher than that, and the main source of energy loss is the poor quality of the perovskite 67 . During cell preparation, perovskite is deposited directly onto the rough Si bottom-cell surface while the electrodes are deposited directly onto the perovskite. This makes obtaining high-quality perovskite difficult. Researchers have proposed the following strategies to improve the quality of perovskite: inserting a buffer layer to protect the perovskite, precursor solution engineering to improve crystalline growth, and passivating the perovskite surface to reduce defects. Similarly, the high roughness of the CIGS subcell surface is a major barrier to the preparation of high-quality uniform perovskite films. In addition to this, the unbalanced efficiency and bandgap mismatch between subcells limits the PCE that can be achieved. Liu et al. 68 greatly improved the efficiency of perovskite with a bandgap of 1.67 eV achieving bandgap and J SC matching with CIGS ( E g = 1.04 eV) through Cl native doping and piperidinium iodide (PDI) surface treatment of CsFAPb(IBr) 3 (Fig. 5a ). As a result, this PSC/CIGS tandem cell obtained the highest PCE of 28.4% to date. For perovskite/organic tandem cells, the low PCE of wide bandgap PSCs is the main reason hindering their development. In recent, Wang et al. 69 reduced non-radiative complexation in wide-bandgap perovskite by a mixed cation (CF 3 -PEA + /EDA 2+ ) passivation strategy. They achieved high V OC (1.35 V) and FF (0.83), which resulted in a record PCE of 24.47% for the perovskite/organic tandem cell. The perovskite/ perovskite tandem cell has been given high expectations due to the lower cost of perovskite compared to the above materials. However, its performance is limited by the high trap density and Sn 2+ oxidation brought by the narrow bandgap perovskite mixed with Sn/Pb. Tan et al. group reported an all-perovskite tandem cell with a 3D/3D bilayer perovskite heterojunction (Fig. 5b ) 66 . This construction with a type II energy band structure at the interface of the perovskite/ETL suppressed interfacial nonradiative recombination and promoted charge extraction. This led to an increase in PCE to 23.8% for single-junction tin-lead perovskite and a maximum PCE of 28.5% for all-perovskite tandem cells. However, the high PCE of the tandem cell is based on high cost. Improving single-junction efficiency and matching between subcells to improve cost-effectiveness is essential.

a (i) Schematic of the 4-T PSC/CIGS tandem solar cell and (ii) the Cl bulk incorporation and PDI surface treatment. Reproduced with permission from ref. 68 Copyright Royal Society of Chemistry. b (i) The schematic structure and (ii) the energy diagram of Pb–Sn PSCs with a 3D/3D bilayer PHJ. Reproduced with permission from ref. 66 Copyright 2023 Springer Nature

In all, by leveraging the defect passivation of perovskite thin films, it is possible to attain high-quality thin films. Besides, conducting thorough optimizations of electrode materials, ETL, and HTL can significantly augment the overall photovoltaic performance of the device. Nevertheless, addressing the interface issue between the functional layers is essential to guarantee the efficiency of photovoltaic devices. Hence, qualified interface engineering holds the key to unlocking the full potential of perovskite photovoltaics, propelling the PCE of PSCs closer to its theoretical Shockley–Queisser limit 70 . Moreover, enhancing the light utilization rate within the device, for instance, by minimizing light reflection, can yield more significant improvements 71 . On the other hand, the concept of TSCs introduces a tangible avenue towards authentic third-generation thin-film photovoltaics, evading the confines of the traditional Shockley–Queisser single-junction limit. Presently, the zenith of achievable PCE in all-perovskite TSCs has ascended to an impressive 28%, while the pinnacle PCE in perovskite/silicon TSCs stands at a remarkable 33.7% 66 . Furthermore, the attainment of higher PCE is attainable through the enhancement of solar energy capture by stacking additional solar cells 72 . By implementing this comprehensive series of optimizations, a substantial improvement in the photovoltaic performance of the device is anticipated.

The stability and improvement strategies

While PSCs have achieved remarkable success in terms of PCE, the significant challenge of ensuring their stability remains a substantial hurdle in the path toward industrialization. PSC device instability stems primarily from two overarching factors: internal issues and environmental influences. The internal factors encompass the structural stability of perovskite, notably addressing both its inherent stability and phase segregation. Meanwhile, environmental considerations encompass aspects such as humidity, oxygen, light, and thermal stability.

Intrinsic factors and strategies

Although single-component perovskites have achieved good results, the thermal stability of MAPbI 3 needs further enhancement. As for FAPbI 3 , despite its more suitable bandgap, the presence of an undesired phase transition poses challenges in maintaining the α phase with active photoelectric properties. Besides, organic-inorganic hybrid perovskites are commonly acknowledged to undergo irreversible decomposition at elevated temperatures, yielding organic halides, lead halides, and other volatile organic compounds. The degradation process results in the collapse of the 3D perovskite structure and the release of organic compounds, adversely affecting device performance. In contrast, CsPbI 3 perovskite demonstrates superior intrinsic resistance to thermal stress, attributed to its exclusion of volatile and degradable components, unlike the volatile MA- and FA-based perovskites. Hence, the thermal stability of all-inorganic perovskite CsPbI 3 is much better than organic-inorganic hybrid perovskite 73 . However, the complicated crystal phases (perovskite phase: α, β, γ phases; non-perovskite phase: δ phase) and their undesirable phase transition will hinder their industrial development. The predominant approach for tailoring optoelectronic properties and ensuring enduring stability in PSCs involves manipulating ions in the A, B, and X sites of a standard ABX 3 perovskite framework. The structure of 3D perovskites can be predicted by the octahedral factor ( μ ) and Goldschmidt’s tolerance factor ( t ) 74 .

where r i is the ionic radii of each ion (A, B, X). Research has revealed that the stable range for metal halide perovskite falls within 0.813 < t < 1.107 as well as 0.377 < μ < 0.895. And 0.8 < t < 1 could be conducive to maintaining the cubic perovskite structure 75 , 76 . Optimal structural stability is attained at t = 1, while any deviation from unity is likely to induce distortion in the BX 6 octahedron. The relationship between the perovskite structure and the t is depicted in Fig. 6a . In the realm of inorganic-organic hybrid halide perovskite materials, an orthorhombic structure typically emerges when the t is below 0.8, while a cubic structure predominates in the range of 0.8 < t < 1. When t surpasses 1, a hexagonal structure tends to manifest. However, a larger A-cation yields the t value exceeding unity, giving rise to a layered perovskite arrangement, exemplified by the Ruddlesden–Popper (RP) phase. Tolerance factors below 0.7 yield non-perovskite structures 77 .

a Correlation between tolerance factor and structure of perovskite crystals. Reproduced with permission from ref. 77 Copyright Royal Society of Chemistry. b Accuracy rate for μ , t , η , ( μ + t ), and ( μ + t ) η to forecast the relative stability of two perovskites. Reproduced with permission from ref. 80 Copyright 2017 American Chemical Society. c Comparison between P(t) and the decomposition enthalpy (∆ H d ) for 36 double perovskite halides. d Schematic diagram for the different periods in the degradation process. Reproduced with permission from ref. 84 Copyright 2018 Wiley-VCH. e The PXRD patterns of CsPbI 2 Br films stored under different humidity conditions and their corresponding photographs Reproduced with permission from ref. 86 Copyright 2022 American Chemical Society. f Device architecture of the PSCs. (Upper left) Schematic diagram of the interaction between F-PDI and perovskite (Right) Schematic diagram of thermal degradation for pristine perovskite and perovskite with F-PDI. (Lower left) Reproduced with permission from ref. 89 Copyright 2019 Wiley-VCH. g SEM images were recorded at different periods for the perovskite films annealed under dry N 2 and low humidity (the scale bar is 1 µm). Reproduced with permission from ref. 91 Copyright 2021 Wiley-VCH

Under the above theoretical background, researchers have optimized the composition to enhance the performance of perovskite, making it exceedingly more suitable for practical applications. Owing to the relatively expansive FA + ion (about 253 pm), the t of FAPbI 3 slightly surpasses 1. Consequently, FAPbI 3 readily assumes the δ phase at standard room temperature conditions. Hence, there arises a need to diminish the tolerance factor of FAPbI 3 while concurrently elevating the activation energy barrier for the phase transition from α to δ phase. Li et al. tried to alloy FAPbI 3 and CsPbI 3 ( t ≈ 0.8). This alloying approach effectively reduced the required treatment temperature for the δ to α phase transition, lowering it from 165 °C for pure FAPbI 3 to below 100 °C for FA 1-x Cs x PbI 3 Consequently, this technique enables precise adjustment of the effective tolerance factor and subsequently bolsters the stability of the α-phase with photoactivity in the composite FA 1–x Cs x PbI 3 alloys 78 . Besides Cs + , the mixture of MA + and FA + , resulting in the creation of FA 1−x MA x PbI 3 , notably enhanced the stability of the α phase. Nazeeruddin et al. made a discovery regarding the enhancement of MAPbI 3 film properties. Through the addition of 10% FA + , they observed a remarkable improvement in both crystallization and compositional uniformity. This enhancement was attributed to the self-organization of the MAPbI 3 film into a stable “quasi-cubic” phase even at room temperature 79 .

Furthermore, the thermal stability for 138 cubic perovskite material was thoroughly investigated through a comprehensive analysis of their decomposition enthalpies (∆ H D ), employing first-principles density functional theory (DFT) calculations. This endeavor yielded a noteworthy discovery: a linear correlation between ∆ H D and the product of ( (t + μ ) η , where η represents the atomic packing fraction. Serving to be an effective thermodynamic stability descriptor, the ( t + μ ) η combination can accurately predict stabilities in halide (chalcogenide) perovskite variants with a commendable precision rate of 86% (90%) (Fig. 6b ) 80 .

Nonetheless, Scheffer et al. uncovered an inadequacy in the predictive precision of t . Their investigation revealed a significant margin of error, nearly one-quarter, in assessing the crystal structure of perovskites by t , particularly in cases involving materials with heavier halides 81 . Hence, the formula of tolerance factor was modified to make it more applicable for materials discovery. The new formula for the tolerance factor is presented below:

where n A is the oxidation state of A. When r A > r B , and τ < 4.18, this material exhibits the perovskite phase. The agreement between the observed values of t and the calculated stability is apparent in 64 out of the 73 materials investigated. Notably, the probabilities generated through classification using t exhibit a linear correlation with the ∆ H d , which proved the value of the monotonic behavior between τ and P(τ) , where the P(τ) is τ -based probability of being perovskite (Fig. 6c ). Using this updated formula, the experimental dataset achieved an impressive overall accuracy of 92%. Hence, drawing upon both Eqs. ( 2 ) and ( 3 ), it becomes feasible to precisely anticipate the crystalline arrangement of a perovskite composition. In the pursuit of cutting-edge photovoltaic applications, the ability to finely manipulate structural attributes holds paramount importance for attaining the pinnacle of efficiency and stability in advanced PSCs.

In the culmination of these endeavors, the strategic intermingling of cations characterized by distinct steric sizes (such as Cs, MA, FA) at the A site, or variations in anions (I, Br, Cl) at the X site, introduces a modifiable effective ionic size. This nuanced adjustment to the tolerance factor ( t ) brings it within a stable range. These empirical principles have provided invaluable guidance in achieving the stabilization of perovskites and in embarking on the exploration of newly emerging and stable perovskites.

External factors and strategies

Alongside intrinsic factors, external environmental factors also wield significant influence over the performance of PSC devices. By encapsulation, PSCs can be effectively prevented from the environmental atmosphere. However, the challenge of realizing an ideal encapsulation necessitates an exploration of the stability of PSCs influenced by environmental factors. The key destabilizing factors for PSCs encompass humidity, oxygen, temperature, and light.

Humidity stability

Based on earlier experimental results, unencapsulated cells underwent degradation in several hundred hours when exposed to air under humidity exceeding 50% 82 , 83 . The phase transition unfolds in a gradual manner, advancing from the grain boundaries toward the interiors of the grains. These dynamic mechanisms are visually depicted in Fig. 6d 84 . As degradation persists, the phase transition extends further into the grain interiors, eventually converting adjacent grains into the non-perovskite phase. Within perovskite crystals, water molecules establish strong hydrogen bonds with organic components. This interaction serves to diminish the bond strength between the organic component and the PbI 6 octahedron, facilitating a more rapid deprotonation of the organic cation. Additionally, water contributes to the protonation of iodide, leading to the formation of volatile HI. Consequently, this process leaves behind PbI 2 as a residue of decomposition 85 . Figure 6e revealed that α-CsPbI 2 Br transit into δ-CsPbI 2 Br at first and decomposed into PbI 2 , which was influenced by relative humidity level and storage time 86 . To bolster perovskite’s humidity stability, two commonly employed strategies are dimension engineering and surface modification.

Dimension engineering is commonly employed to enhance humidity stability and strengthen the activation energy barrier. Two-dimensional (2D) perovskites demonstrate notable stability but exhibit limited PCE. To concurrently boost both the PCE and stability, a new era of mixed-dimensional (MD) perovskite has emerged. Zheng et al. orchestrated MD perovskite by incorporating HOCH 2 CH 2 NH 3 I (EAI) into the (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 3D perovskite. Upon enduring exposure to approximately 50% relative humidity for more than 1700 h, unencapsulated devices preserved approximately 85% of their initial PCE when incorporated with EAI. However, the 3D perovskite film degrades after 400 hours of storage and swiftly transforms into yellow PbI 2 within a brief period in a humid environment. This marked improvement is ascribed to the exceptional crystal structure and surface morphology 87 . Li et al. engineered a novel heterostructure, termed Localized Dion-Jacobson (DJ) 2D–3D Heterostructures (L2D–3DH), by selectively growing the DJ phase on 3D perovskite films. This selective growth, achieved through post-treatment with divalent organic spacer cations (1,4-butanediamine iodide), enhances grain boundary passivation and prevents moisture penetration. Unlike conventional 2D–3D composites, this design minimally hinders charge extraction due to exposed 3D regions, eliminating the need for precise orientation control. PSCs based on L2D–3DH demonstrated remarkable advancements, reaching a PCE of 20.1%, slightly surpassing pure 3D-based PSCs (19.7%). Enhanced PCE is attributed to DJ 2D plate-induced grain boundary passivation, reducing trap density and non-radiative recombination. Impressively, L2D–3DH-based PSCs exhibit extended stability under high moisture without full 2D film coverage. Initial PCE of 86% reserved with unencapsulated L2D–3DH-based PSCs after 1300 hours under 70% RH, outperforming 3D counterparts at 56%. Under heat and high humidity stress, an initial PCE of 75% was reserved with L2D–3DH-based PSCs after 200 hours of continuous aging at 80 °C and 70% RH 88 .

Passivating grain boundaries and modifying the surface of perovskite can also mitigate moisture-induced degradation of the perovskite layer. Yang et al. incorporated N, N’-bis-(1,1,1,2,2,3,3,4,4-nonafluorododecan-6-yl)-perylenediimide (F-PDI) into perovskite, resulting in defect passivation and the formation of a hydrophobic structure, and thereby remarkable enhancing photovoltaic performance and device stability. The carbonyl groups in F-PDI chelated with uncoordinated Pb 2+ , which led to defects passivation at grain boundaries and the perovskite surface. The F-PDI molecules with strong conductivity facilitated charge transfer across grain boundaries, enhancing photovoltaic properties. Additionally, hydrogen bonding between fluorine groups and MA could fix the MA + ion (Fig. 6f ). Notably, the inherent hydrophobicity of F-PDI shielded perovskite from moisture, substantially bolstering humidity resistance in PSCs 89 . Zhan et al. introduced a versatile self-encapsulation method for crystal growth using polymer-assisted bottom-up dynamic diffusion. A polymer scaffold formed during nucleation and is subsequently etched by the anti-solvent, guiding perovskite growth. This approach balanced nucleation density and growth rate, enhancing crystalline quality by preventing excessive precursor-polymer interaction. The dynamic diffusion involved polymers in nucleation and growth, resulting in controlled nucleation and phase separation-driven encapsulation. The distribution of polymers such as polyethylene glycol (PEG) or polystyrene (PS) at surface, grain boundaries, or buried interfaces sequentially passivated defects, aligned energy bands, and aided carrier transportation, yielding PSCs with high V OC (1.15 V), FF (80.72%), and PCE (22.90%). Moreover, self-encapsulated PSCs exhibited remarkable environmental stability, with negligible decomposition and 90% PCE retention after 90 days under 30-50% humidity in ambient air 90 .

While perovskite degradation transpires in high humidity conditions, empirical investigations have demonstrated that perovskite films can self-heal defects through exposure to mild humidity. Figure 6g portrays the dynamic transformations of film morphology during the annealing process under dry (DR) and low humidity (LHM) atmospheres (30-40% relative humidity). Initially, the film exhibited an uneven morphology with small and irregular grains (DR-0 min). Once exposed to LHM, the grains grew larger with better uniformity (LHM-0 min), signifying a moisture-induced phase transition. Throughout annealing, both atmospheric conditions led to grain size augmentation and textured surfaces, attributed to perovskite crystal growth. Notably, for the DR scenario, annealing resulted in numerous pinholes (DR-1 min), persisting in the final DR-perovskite film. In contrast, LHM annealing produced fewer pinholes (LHM-1 min), subsequently diminishing during the process. The ex-situ SEM observations validated the gradual healing of pinholes and defects in FA-based perovskite films directly through humidity-annealing. In device application, films prepared under LHM exhibit optimal PCE, primarily due to enhanced V OC and FF. Further optoelectronic analyses confirmed that improved device performance stems from reduced defects in the film. These experimental findings underscored that humidity operated as a two-edged sword. Reasonable humidity tuning can enhance the performance of PSCs significantly 91 .

Oxygen stability

Some experiments have shown that metal halide perovskites could exhibit relative stability to oxygen when kept in the dark, suggesting their fair stability in the ground state 92 , 93 . However, upon light exposure, the MAPbI 3 perovskite layer undergoes rapid degradation. Oxygen can trigger the degradation of perovskite film in specific circumstances. As shown in Fig. 7a , there is a schematic illustration of the photo-oxidative degradation process of the MAPbI 3 (001) surface. Step I involves the interaction between the O 2 near the surface of MAPbI 3 and the photo-excited electrons from MAPbI 3 . This interaction resulted in the formation of superoxide (O 2 − ). For Step II, these O 2 − undergo a reaction with [CH 3 NH 3 ] + ions and Pb atoms, leading to the production of H 2 O and Pb(OH) 2 on the surface terminated with MAI, thereby exposing the underlying MAI-terminated surface. In Step III, the oxidation products generated in the previous steps restrain the oxidation of the inner MAPbI 3 . Next, the water molecules contribute to the hydration of the inner perovskite structure. As a result of this hydration process, the inner perovskite gradually disintegrates, leading to the breakdown of the entire perovskite structure over time 94 , 95 , 96 , 97 . What’s more, oxygen has the potential to oxidize metal oxide charge transport materials, particularly TiO 2 . TiO 2 is notably susceptible to reacting with ambient oxygen, resulting in the formation of superoxide, which then contributes to the oxidative degradation of perovskite 98 , 99 .

a Diagram illustration of the photo-oxidative degradation mechanism of the MAPbI 3 (001) surface. Reproduced with permission from ref. 97 Copyright Royal Society of Chemistry. b Schematic depicting the shift from non-radiative recombination (k n ) dominance due to the presence of shallow surface states, to radiative-dominant recombination (k R ) following the removal of these states through treatment. Untreated MAPbI 3 film c (i) comprising non-radiative trap states which are passivated upon MAPbI 3 exposed to (ii) light and oxygen and (iii) light, oxygen, and water. Reproduced with permission from ref. 102 Copyright 2017 Elsevier Ltd. d PL intensity as a function of time in vacuum and on exposure to dry N 2 , dry CO 2 , and dry Ar. e PL intensity as a function of time on exposure to air, dry O 2 , and moist N 2 . Reproduced with permission from ref. 103 Copyright 2016 American Association for Advancement of Science. f Characteristics of devices utilizing both the reference film and the air-CsPbI 2 Br film. Dark current-voltage measurements were conducted on electron-only devices. Reproduced with permission from ref. 104 Copyright 2019 American Chemical Society

To diminish the adverse effect of oxygen on device performance, the incorporation of a 2D layer proves to be a notably effective approach. Shao et al. demonstrated that the incorporation of a small amount of 2D tin perovskite into a 3D tin perovskite led to an enhancement in the crystallinity of 3D FASnI 3 . The extended arrangement of crystal planes has significantly fortified the resistance ability and structural integrity of the perovskite framework, concurrently mitigating tin vacancies and minimizing background carrier density. The substantial crystalline quality and preferential orientation significantly underlie the improved solar cell performance. Moreover, device stability under non-encapsulated ambient conditions (humidity ~20%, temperature ~20 °C) was assessed. The device employing a hybrid 2D/3D structure exhibited significantly greater stability in comparison to its pure 3D counterpart. Following a 76-hour exposure to ambient air, the pure 3D perovskite device experienced a complete failure. Conversely, the 2D/3D composite device demonstrated remarkable resistance by preserving an impressive 59% of its initial PCE. Further XRD measurements were performed on perovskite samples stored in nitrogen atmosphere and ambient air. The 3D and 2D/3D samples decomposed slightly after 6 hours in an inert atmosphere. Notably, the 3D sample exhibited much quicker chemical degradation than the 2D/3D sample when exposed to ambient conditions. This enhanced ambient stability of the 2D/3D-based device was likely attributed to heightened resistance ability to oxygen and moisture, stemming from improved crystallinity and higher perovskite film hydrophobicity 100 .

While the presence of oxygen can substantially weaken the chemical stability of perovskite materials due to reactions with protonated organic cations like MA + and FA + , it’s important to highlight that leveraging oxygen for defect passivation has also arisen as a potent and convenient strategy in suppressing nonradiative recombination processes and bolstering the photovoltaic performance of PSCs by strongly interacted with halide vacancies located on the perovskite surface 101 . The mechanism of photo brightening is given in Fig. 7b . After being treated by light, O 2 , and humidity, the density of the shallow state below the conduction band will decrease, leading to the increase of the radiative bimolecular recombination (k R ) and decrease of non-radiative bimolecular component (k n ), which significantly enhance the photoluminescence quantum yield (PLQY). The detailed passivation mechanism is as follows: Initially, an untreated MAPbI 3 sample with surface states (Fig. 7cii ) was subjected to illumination in the presence of O 2 . This illumination-induced process made a reduction to the density of surface states as well as triggered photo brightening, as depicted in Fig. 7cii ). The mechanism behind this phenomenon involved the formation of passivating superoxide species. Importantly, the transformation was reversible and occurred in several hours when subsequently shielded from light. Subsequently, an untreated sample was momently subject to both illumination and a combination of H 2 O and O 2 (Fig. 7ciii ). In this case, the reduction in the density of shallow states became much more pronounced owing to the complete elimination of surface states. This elimination resulted from the formation of a nanometer-thin amorphous shell composed of inert degradation products. This process is nearly irreversible, and the shell of degraded material effectively serves as a containment barrier by which oxygen species can just tardily escape from the film. These treatments effectively reduce ion migration, as oxygen molecules occupy iodide vacancy sites integral to the ion migration process. Moreover, the presence of the degraded shell introduced a partial impediment to ionic transport within the intergrain regions 102 . Fang et al. explored the change in PL intensity over time for a single crystal while exposed to various gas atmospheres during illumination (Fig. 7d, e ). The PL intensity of the crystal remains unaffected when exposed to dry N 2 , CO 2 , or Ar. However, a significant and swift increase in PL intensity occurred in the presence of air, dry O 2 , and humidified N 2 . It’s noteworthy that the most rapid and pronounced enhancement in PL intensity was observed when the crystal was exposed to air. In contrast, the recovery of PL intensity was notably slower in the case of dry O 2 and humidified N 2 . These observations highlighted the role of molecular properties, specifically those of O 2 and H 2 O, in driving the PL enhancement, which is consistent with the mechanism mentioned above 103 . Unlike the conventional method of oxygen molecule passivation via surface physisorption on perovskites, Liu et al. discovered that individual oxygen atoms offer superior passivation because of the stronger interaction with perovskite. Crucial to attaining this objective is dry-air processing, dissociating O 2 into O during annealing. O-passivated inorganic halide PSCs exhibited less density of defects, higher PV performance and improved air stability compared to O 2 -passivated devices, as shown in Fig. 7f 104 .

Light stability

Although environmental variables like oxygen and humidity can be addressed through encapsulation, it’s imperative for the solar cell to maintain its light stability over extended periods. Light-induced phenomena significantly influence perovskite materials, primarily manifesting as halide segregation, ion migration, and triggering irreversible photochemical reactions 105 , 106 , 107 .

When subjected to AM 1.5 G solar simulator illumination, the photoluminescence intensity of MAPbI 3 undergoes a strong enhancement in the beginning, accompanied by a drastic reduction in trap density under the influence of light 106 , 108 . This reduction translates into an augmented photovoltage within the device. The heightened photoluminescence intensity can be ascribed to the migration of I-species away from the irradiated zone. During the film formation process, specific regions exhibited a higher concentration of electron traps, likely stemming from iodine vacancies and associated interstitial iodine ions, which predominantly existed at the surface and grain boundaries, as shown in Fig. 8ai . Upon exposure to light, a notable density of light-excited electrons and holes emerges, most concentrated at the surface and gradually declining through the film. A considerable number of these light-excited electrons tend to be trapped, particularly in proximity to surfaces (Fig. 8aii ). Trap filling perturbs the system, generating an electric field that triggers iodide migration. This migration leads to trapping annihilation through various mechanisms, including coulomb repulsion between unscreened iodide ions currently, space charge separation due to surface-trapped electrons and diffused holes, and alterations in surface band bending under illumination. The resultant induced migration facilitates the movement of numerous mobile iodides to occupy the vacancies, ultimately reducing the density of vacancies and interstitials (Fig. 8aiii ). Once removing the light, the profile of light-excited components dissipates, leaving some residual traps. This residual state allows for gradual lateral or vertical migration of iodides to establish a new equilibrium over time (Fig. 8aiv ), resulting in a partial reversibility 107 .

a (i) The density of traps within a ‘dark spot’ is notably elevated, accompanied by an excess of iodide ions at first. (ii) Upon exposure to light, electrons rapidly occupy traps, generating an electric field that prompts the migration of iodide away from the illuminated area, subsequently occupying the vacant positions. (iii) The system ultimately attains a stable emission output, accompanied by a diminished trap density and iodide concentration within the illuminated area. (iv) After the removal of illumination, concentration gradients may facilitate the return of some iodide back into the dark spot before eventually establishing a new equilibrium with a redistributed iodide profile. Reproduced with permission from ref. 107 Copyright 2016 Springer Nature. b Maximum power output tracking was conducted on three identically prepared PSCs, designated as devices A, B, and C, while exposed to UV-filtered 1 Sun equivalent light. Devices A and B were continuously monitored for more than 100 h, whereas Device C underwent cyclic tracking four times, with each tracking session lasting 5 h, interspersed with periods of being kept in the dark at an open circuit. Schematic illustrations were employed to visualize the evolution of ion distribution within the perovskite layer situated between the electron and hole selective contacts during the operational conditions of the solar cells: c (i) initial conditions, (ii) non-stabilized conditions in several minutes, and (iii) the stabilized condition in several hours. Reproduced with permission from ref. 109 Copyright Royal Society of Chemistry. d Theoretical simulation involving the incorporation of BD molecules into FA perovskites—illustrating the procedure for creating a stable surface structure of FAPbI 3 with BD molecules. Reproduced with permission from ref. 114 Copyright 2023 Elsevier Ltd. e Illustrations depicting the structural configurations of MAPbI 3 and (5-AVA) x MA 1-x PbI 3 within triple-mesoscopic layers, along with the mechanisms of material decomposition and ionic migration triggered by the combined influence of light, heat, and electronic bias. The green insets offer details regarding the Pb-I bond lengths and I-Pb-I bond angles within MA + -terminated slabs (left) and 5-AVA + -terminated slabs (right), respectively. Reproduced with permission from ref. 115 Copyright 2020 Elsevier Ltd

When considering the deterioration caused by light exposure in photosensitive materials, it becomes crucial to take into account irreversible chemical reactions triggered by light. This process, known as photoinduced degradation, comprises two distinct phases: the first is a rapid degradation process that can be reversed, which is referred to as regime I), while the second is a slower degradation process that is irreversible (referred to as regime II), as shown in Fig. 8b . Domanski et al. conducted an extensive investigation involving the continuous monitoring of the maximum power output from three identical devices labeled as A, B, and C. Devices A and B underwent continuous monitoring for a duration exceeding 100 hours. Notably, device A exhibited a relatively unstable performance, while device B owned good stability. It’s worth highlighting that both devices shared an identical time constant during the decay regime I. To distinguish and study regime I independently from the following degradation, specific measures were taken for device C. In this regard, the maximum power point tracking (MPPT) for device C was intentionally paused after just 5 h of operation. Subsequently, the tracking was periodically re-initiated following periods of rest in darkness, with the duration of these resting periods being intentionally varied.

In relation to regime I, it is important to notice that both halide and cation vacancies possess mobility within the material, although cation vacancies exhibited slower mobility compared to halide vacancies. The distribution of these vacancies within the perovskite layer significantly influences the extraction of charges and consequently impacts the overall PCE of the device. Figure 8ci–iii illustrated the arrangement of halide lattice within the perovskite with ionic vacancies. The initial scenario (Fig. 8ci ) depicts a balanced presence of anion and cation vacancies, randomly dispersed throughout the perovskite lattice (Fig. 8cii ). Up to 100 seconds (equivalent to minutes), following the initiation of light exposure and the transition to the MPPT, halide vacancies migrate, forming a Debye layer at the interface with the hole-selective contact, while cation vacancies, with comparatively limited mobility, remain behind (Fig. 8ciii ). As the timeframe extends beyond 1000 seconds (equivalent to hours), cation vacancies accumulate, forming an additional Debye layer at the interface with the electron-selective contact. This accumulation of cation vacancies impedes the extraction of charges from the device, contributing to the loss of efficiency. Consequently, under realistic operational conditions, the gradual migration of ions emerges as the underlying cause of reversible losses within the device over hours. When the device is allowed to recuperate in darkness for several hours, the distribution of ionic vacancies reverts back to its initial state 109 .

In the context of regime II, the irreversible process can be attributed to a chemical degradation reaction. Following an extended period of exposure to white light, the MAPbI 3 film undergoes a transformation into MAI and PbI 2 . Over the course of 6 hours, PbI 2 is liberated and subsequently disintegrates into Pb and I 2 . As the duration of light exposure reaches 24 hours, the decomposition process reaches saturation, establishing a self-limiting mechanism. However, these degradation products induce a bending of the band at the interface, introducing a constraint on carrier transport 110 , 111 .

When subjected to ultraviolet light, the N-H bonds within the perovskite lattice dissociate, leading to the generation of CH 3 NH 2 and H 2 . Following a period of 2 hours, metallic Pb emerges as a result of decomposition, which progresses and eventually reaches a state of saturation. This intricate process of degradation under ultraviolet irradiation further underscores the dynamic behavior of the MAPbI 3 film, influencing its structural integrity and performance characteristics 112 .

To address the challenge of prolonged instability, researchers are consistently making dedicated endeavors. Liu et al. have introduced a covalent bonding strategy utilizing bis-diazirine (BD) molecules to form robust covalent bonds with the organic cations in perovskite materials, which could crosslink aliphatic organic molecules which contain C–H, O–H or N–H bonds via high temperatures or UV light to activation of diazirine groups 113 . What’s more, the separation between the binding sites of BD molecules (9.20 Å) closely corresponds to the lattice size of FA perovskite (9.01 Å). Both experimental findings and ab initio simulations validate the remarkable effectiveness of BD molecules in firmly immobilizing these organic cations (Fig. 8d ). As a result, the thermal, illumination, and electrical bias resistance properties of perovskites are significantly enhanced. This advancement has resulted in the achievement of exceptionally efficient PSCs, boasting a remarkable efficiency of 24.36%. Notably, these ultra-stable PSCs maintain 98.6% of their initial efficiency even after undergoing 1000 h of operational testing 114 . Han et al. have discerned that the primary cause of deterioration in MAPbI 3 perovskite lay in the liberation of MAI at grain boundaries within an exposed area or the crystal’s reshaping within confined spaces (Fig. 8e ). Furthermore, irreversible long-distance ionic migration was induced by the combined influences of light, heat, and electrical bias. By fortifying the grain boundaries with a bifunctional organic molecule, 5-ammoniumvaleric acid (5-AVA) iodide, the crystalline structure of MAPbI 3 can be fixed on a nanoscale. Consequently, the disintegration or reshaping of the crystal was suppressed, and the ionic migration became reversible. This method provided a dependable way to meet IEC61215:2016 stability requirements for PSCs. Remarkably, a printable PSC embedded with (5-AVA) x MA 1-x PbI 3 has demonstrated its endurance, functioning for over 9000 h at a maximum power point of 55 °C ± 5 °C, with no discernible degradation 115 .

Thermal stability

Given the necessity of high-temperature both in annealing for perovskite film and subsequent module encapsulation, coupled with the requirement for long-term stability at 85 °C for solar cells, enhancing the thermal stability of PSCs becomes imperative for their successful industrial implementation 116 , 117 . The exceptional light-harvesting capabilities of MAPbI 3 progressively diminish with time as it transforms into PbI 2 after the escape of MAI 118 . Zhu et al. depicted defect types and ion migration in inverted MAPbI 3 PSCs with a schematic diagram (Fig. 9ai-iv ). Primary Schottky defects include MA vacancies (V MA ) and I vacancies (V I ), while vacancy defects for Pb 2+ are less owing to high energy barriers for their formation. Consequently, ion migration, particularly of MA + and I − , is probable at room temperature, while Pb 2+ migration requires thermal excitation. This migratory process intensifies at 85 °C, leading to the formation of PbI 2 as MA + ions escape. Additionally, reducing the I/Pb ratio on the MAPbI 3 surface results in the emergence of metallic Pb 0 defects (Fig. 9ai ), and Pb ion migration is observed during continuous thermal aging (Fig. 9aiii )) Schottky defects often coincide with Frenkel defects as interstitial ions pair with vacancies (Fig. 9aiv ) 119 . These ion migrations and defect accumulations at elevated temperatures contribute to structural changes in MAPbI 3 perovskite materials, leading to device degradation 120 . What’s more, perovskite films can also degrade at lower temperatures over extended durations due to the volatilization of halide species and the organic cation, particularly when MA-containing compounds are involved 117 . As such, there is a pressing requirement to enhance the thermal stability of organic/inorganic hybrid perovskites.

Illustration depicting ion migration and defect types in MAPbI 3 following heating at 85 °C. Schottky defects: vacancy defects and migration of a (i) MA + , (ii) I − , (iii) Pb 2+ , and (iv) Frankel defects. Reproduced with permission from ref. 120 Copyright 2023 Elsevier Ltd. b Top-view SEM images: 2MBI-modified perovskites pre/post thermal degradation after 3 days storage and normalized PCE of devices across multiple heat treatment cycles. Reproduced with permission from ref. 125 Copyright 2022 American Chemical Society. c Performance evolution of the highly stable control and DDT-treated devices during thermal stress over 144 h. Insets: photographs of the control sample (left) and DDT-treated sample (right). Reproduced with permission from ref. 131 Copyright 2022 Springer Nature. d Schematic representation of the encapsulated device. Reproduced with permission from ref. 136 Copyright Royal Society of Chemistry

Research has demonstrated that utilizing a blend of MAI and FAI in films created through a two-step deposition method, with MAI content below 20%, contributed to the trigonal phase maintaining its structural integrity across the studied temperature range (25 to 250 °C) 14 . Moreover, the slight introduction of MAPbBr 3 to MAPbI n Br 3–n can enhance both PCE and thermal stability 121 . Besides crystallization optimization, dimension engineering or surface modification can also improve the thermal stability of perovskite 122 , 123 , 124 . For example, the application of a conjugated sulfide known as 2-mercaptobenzimidazole (2MBI) yielded remarkable enhancements in the PV characteristics and thermal stability of perovskite. During thermal processing, 2MBI formed interconnections on the perovskite surface, thereby facilitating the movement of charges, curbing the release of volatile components, and orchestrating the rearrangement of surface perovskite crystals. The PSCs modified by 2MBI attained a PCE of 21.7%, maintaining consistently impressive yield even while undergoing and following exposure to a temperature of 85 °C (Fig. 9b ). In contrast, unmodified PSCs experienced significant degradation under similar conditions. Furthermore, unencapsulated devices, following thermal stress, maintained more than 98% of their initial efficiency after a 40-day storage period under ambient environmental conditions 125 .

Heightened temperatures not only lead to the degradation of perovskite but also affect the performance of the charge transport layer. Charge transport layers composed of inorganic metal oxides, such as TiO 2 and NiO x , typically exhibit robust thermal stability owing to their high decomposition temperatures. However, in comparison, the organic charge transport layer’s thermal stability significantly lags behind that of its inorganic charge transporting layers 126 , 127 , 128 . For instance, iodine migration into Spiro-OMeTAD was observed when subjected to a 50-hour thermal treatment at 85 °C in an argon environment. This migration led to a reduction in oxidized Spiro-OMeTAD and subsequently lowered the conductivity of the transport layer 129 . To enhance the stability of Spiro-OMeTAD, additive engineering has proved to be an effective strategy. Based on the fundamental requirement of introducing a lithium compound (LiTFSI) for chemical doping to achieve satisfactory conductivity and efficient hole extraction in spiro-OMeTAD, Liu et al. incorporated an economical alkylthiol additive (1-dodecanethiol, DDT) into the spiro-OMeTAD HTL. Through the inclusion of DDT, a more effective and finely controlled doping procedure emerges, considerably reducing the duration of doping. This advancement empowered the HTL to attain comparable performance levels even before exposure to air activation. The synergy between DDT and LiTFSI enhanced the dopant concentration within the bulk of HTL. Consequently, it diminished dopant accumulation at interfaces and bolstered the overall structural resistance ability of HTL when subjected to conditions such as moisture, heat, and light exposure. Impressively, these devices exhibited remarkable durability, retaining 90% of their peak performance over a continuous 1000-h illumination period. The study delved into the effect of DDT on thermal stability, conducted through thermal stress experiments on unencapsulated PSCs. Notably, Fig. 9c illustrated a substantial increase of up to 63% in peak PCE at 50 °C after 120-h for the finest control device, which resulted from a drastic reduction in trap density under the influence of light 130 . In contrast, the most superior DDT-treated device displayed exceptional performance retention, up to 95%, during the same measurement interval. Subsequent evaluation at an elevated temperature of 85 °C revealed a speedier 16% deterioration for the control device after 24 h, while the DDT-treated device exhibited a more gradual decline, with only an additional 5% reduction 131 . Some other strategies have also been proposed to improve the thermal stability such as interface engineering or synthesis of new HTL materials 132 , 133 , 134 , 135 .

Additionally, through the adept application of suitable encapsulation methodologies, PSCs can endure even the most challenging environmental conditions (Fig. 9d ). To delve deeper into the intricate chemistry of perovskites within operational PSCs, it is imperative to establish stringent encapsulation procedures that effectively shield against the impact of ambient air 136 , 137 , 138 .

To enhance the stability of PSCs, a comprehensive strategy should be implemented, incorporating a range of improvement measures. Initially, the optimization of materials and the fine-tuning of the perovskite formula are pursued to fortify its long-term stability. Subsequently, state-of-the-art encapsulation technology is employed, utilizing moisture-resistant, anti-oxidative, and UV-resistant materials to alleviate the impact of the external environment on the cell. Within the device structure, interface engineering is deployed to enhance interactions between layers, minimizing interface defects and elevating overall stability and performance. The use of appropriate ion migration inhibitors prevents the uncontrolled movement of charge carriers within the device, thereby retarding the aging process. Finally, the continual refinement of the production process ensures heightened production consistency, guaranteeing the stability and performance of each individual solar cell. These integrated enhancements collectively contribute to an augmented overall stability of PSCs.

Large-scale fabrication

While PSCs have showcased remarkable advancements in small-scale devices, bridging the disparity between laboratory efficiency and large-area devices remains to be a significant challenge. Up to now, the highest efficiency in PSCs has commonly been achieved through a spin coating-based fabrication method. Nevertheless, this particular approach faces significant industrial scalability challenges, primarily stemming from the non-uniform perovskite thin films from center to edge 139 . Additionally, the spin coating process suffers from an exceptionally low material utilization ratio, posing a substantial hindrance to its broader implementation within industrial-scale production endeavors 140 . A multitude of industrially viable alternatives to spin coating methods have been investigated, including doctor blade coating, spray coating, slot-die coating, inkjet printing, and screen printing. These diverse techniques have shown remarkable compatibility with industrial processes, and as a result, substantial advancements have been achieved in the upscaling of PSCs.

Different fabricating techniques

In the blade-coating procedure, the initial step involves positioning the substrate onto heated platforms. A specialized blade is then employed to evenly distribute the precursor solution across the substrate’s surface, creating a uniform wet film. The efficacy of this process relies on precisely calibrating the solution’s wettability, thereby enhancing its capacity to coat the substrate comprehensively. As the solvent gradually evaporates, the solute within the solution crystallizes onto the substrate, culminating in the formation of perovskite film. Typically, subsequent annealing is necessary to facilitate crystallization 141 . The quality of the perovskite film is determined by the crucial factors of blading speed, distance between the blade and the substrate, wettability of the substrate, ink viscosity, blading temperature, and crystallization control. In addition to fundamental parameters, the introduction of a nitrogen knife (N 2 -knife) in blade coating expedites the drying of wet films at room temperature (Fig. 10a ). It exhibits distinct advantages including room temperature and high-speed coating capabilities. Simultaneously, it generates superior perovskite films with enhanced uniformity and smoothness, even on large-scale substrates, consistently. Precise control of gas blowing conditions—such as gas pressure, nozzle angle, and airflow—is pivotal to this process 142 . The blade coating method offers several benefits over the spinning coating technique for fabricating large-area modules. These advantages include the efficient use of raw materials, the feasibility of preparing in open-air environments, an extended reaction window, and the capability for continuous deposition using Roll to Roll (R2R) and Sheet to Sheet (S2S) processes, underlining its substantial potential for advancement. However, while the extended reaction window in the blade coating method facilitates the growth of perovskite grains, leading to larger grain size, the challenge lies in forming a film free of needle holes during natural drying, primarily due to the slow evaporation of solvents. In recent years, researchers have been diligently working to overcome these challenges. Nowadays, the highest PCE by a blade coating method is 24.31%, which was achieved by a novel pre-seeding approach that involves blending FAPbI 3 solution with pre-synthesized MAPbI 3 microcrystals. It can effectively decouple the nucleation and crystallization with the N 2 -assisted blade coating method. Consequently, the initiation of crystallization extends impressively threefold (from 5 s to 20 s), facilitating the creation of homogeneous alloyed-FAMA perovskite films with precise stoichiometric ratios 143 . The largest active area achieved by the blade coating method is 100 cm 2 144 .

Schematic illustrations. a Air-knife-assisted blade-coating. Reproduced with permission from ref. 142 Copyright 2020 Zhengzhou University. b Megasonic spray-coating. Reproduced with permission from ref. 294 Copyright 2018 Wiley-VCH. c Slot die coating. Reproduced with permission from ref. 150 Copyright 2021 Wiley-VCH. d Inkjet-printing: (i) continuous inkjet printing (CIJ), ( ii ) drop-on-demand (DOD) inkjet printing. Reproduced with permission from ref. 158 Copyright Royal Society of Chemistry. e Screen printing. Reproduced with permission from ref. 140 Copyright 2018 American Chemical Society

Spray coating emerges as a promising technique for upscaling perovskite film fabrication (Fig. 10b ). This approach relies on droplets overlapping during contact with the substrate, ensuring uniform film deposition even on curved and non-flat surfaces. The spray coating process unfolds in four distinct stages: droplet generation, droplet transport across the substrate, droplet coalescence into a wet film, and the subsequent drying of this film 145 . Essential spray process parameters, such as substrate temperature, spray head-to-substrate distance, spray head movement speed, and precursor solution dispensing rate, remain consistent across different droplet generation mechanisms. The resultant film morphology is intricately tied to these parameters. Notably, droplet size, ink composition, deposition temperature, drying time, and trajectory significantly influence the formation and overlapping of droplets into thin films 146 . Hence, achieving high-quality perovskite films through spray coating necessitates meticulous control of parameters. Furthermore, a primary drawback of the spray coating method is that newly sprayed droplets tend to dissolve the already-formed film, adversely impacting the quality of the final film coverage. Additionally, the sputtered droplets from this process pose a risk of contaminating the production environment. At present, The highest PCE by a spray coating method is 24.31%, which was achieved by a combination of three key technologies, viz high-performing SAM hole-transport layers, ultrasonic spray coating, and gas-assisted quenching 147 . The largest active area achieved by the spray coating method can reach 112 cm 2 148 .

In slot-die processing, the quality of wet films is determined by the precision of the meniscus formation (Fig. 10c ). The distance between the slot-die head and the substrate impacts film thickness, while the balance between pumping rate and coating speed influences coverage, roughness, and uniformity. To expedite wet film drying, slot-die coating facilities incorporate supplementary air-knife or hot-stage features to emulate a quenching effect 149 , 150 . Furthermore, gas, anti-solvent, and vacuum-assisted quenching techniques prove valuable in achieving large-area films that are uniform, pinhole-free, and consistently homogeneous 151 , 152 , 153 . In contrast to alternative upscaling methods, slot-die coating stands out for its remarkable system compatibility. It seamlessly adapts to both S2S and R2R systems 154 . The slot-die coating method offers distinct advantages over the blade coating technique, particularly in the handling and application of perovskite ink. In this method, the ink is securely stored in a tank, maintaining its viscosity and concentration consistently throughout the coating process. This stability allows for precise control over the film thickness, achieved by adjusting a combination of factors such as the ink’s concentration and viscosity, the distance between the coating head and the substrate, as well as the speeds of both coating and inking and the air-knife pressure. These variables can be meticulously set and programmed in advance. Additionally, a significant benefit of the slot-die method is its non-contact nature; the coating head does not need to touch the base, thereby avoiding potential scratches or damage to the substrate during application. However, to enhance the preparation of superior perovskite films through the slot-die coating method, there is a requirement for more comprehensive studies on fluid dynamics and the design of slot-die apparatus. Up to now, the highest PCE with the slot-die coating method is 23.4%, which is achieved by surface redox engineering for electron-beam evaporated NiO x . This strategy not only resolves the issue of local de-wetting in perovskite ink but also significantly boosts the electronic properties at the buried interface by carefully adjusting the surface characteristics of NiO x 155 . The largest active area achieved by the slot-die coating method is 300 cm 2 156 .

Inkjet printing stands as a versatile deposition technique, adapted for creating functional layers using consistent molecular or colloidal liquid phase inks. This process functions by expelling ink droplets from a nozzle, allowing for controlled properties and meticulous deposition on a target substrate, ultimately leading to precise fixation. In the realm of inkjet printing, two prevalent techniques have been extensively utilized for generating ink droplets: (i) continuous inkjet printing (CIP) (Fig. 10di ) and (ii) drop-on-demand (DOD) inkjet printing (Fig. 10dii ) 157 , 158 . The inject printing method proves highly efficient for producing large-area perovskite films. However, one of the foremost challenges in manufacturing solar cells through inkjet printing technology is developing an ink that not only has the right viscosity and wettability but also maintains long-term stability. Critical to this process is solvent engineering, which involves carefully choosing the ideal solvent or solvent mixtures to achieve the desired ink formulation, taking into account different solubility factors. Additionally, a major hurdle to overcome for the broader adoption of high-resolution inkjet printing is the prevention of nozzle clogging, especially given the need for nozzles with very narrow diameters to achieve high printing accuracy. At present, the highest PCE with the inject printing method is 20.7%, achieved by the oxygen atmosphere tuning during the deposition process and the layer thickness optimization, where the average absorptance of NiO x is just 1% 159 . The largest area with the inject printing method is 804 cm 2 , with a PCE of 17.9% 160 .

In the realm of screen printing, a squeegee exerts pressure to transfer paste onto a substrate through openings in a meticulously patterned mesh screen, crafted from either fiber or steel mesh (Fig. 10e ). The final thickness of the printed films hinges on factors such as mesh size, screen thickness, and the paste material ratio. Screen printing stands out as a fast and flexible method for transferring diverse patterns onto a variety of substrates. It is highly compatible with different functional layers, offering considerable flexibility in pattern design and scalability. This method holds great potential for a wide range of applications. Up to now, the highest PCE with inject printing method is 20.52% 161 . The largest area with the screen printing method is 198 cm 2 162 .

The description provided suggests that various fabrication techniques lead to differing gaps between the lab PCE and PSM. In the next section, we focus on elucidating the considerations surrounding the scaling-up factor and the associated cost factor pertaining to PSM.

Some factors in PSM

The increase in the perovskite film’s surface area corresponds to a higher defect density and diminished film uniformity, ultimately resulting in a decline in the photovoltaic performance of PSM. When contrasting the photovoltaic performance of films with varying sizes, it is difficult to make a fair and consistent comparison of their performance disparities. Hence, formula (4) served as the means to ascertain the scaling-up factor ( f scaling-up ), a pivotal determinant in gauging upscaling losses 163 . The formula is presented below:

where η is the PCE, and A is the active area of the cell or module. The lower the value of f scaling-up , the less amplification loss occurs from PSCs to PSM, making it increasingly favorable for the industrial advancement of PSM technology. The highest lab PCE of PSCs and the PCE of the biggest area of PSM up to now are shown in Table 1 .

From Table 1 we can find that the value of f scaling-up for inject printing is the lowest, which indicates the amplification loss can be effectively minimized by inject printing method. In the course of amplifying devices, a loss of efficiency is inevitable. Consequently, the pressing challenge remains to develop a PSM that is both compatible with large areas and capable of achieving high efficiency. By contrast, the PCE of silicon heterojunction solar cells reached 26.81%, with an area of 274.4 cm 2 164 . While the PCE of PSCs has rapidly approached that of silicon solar cells, a significant disparity in the context of large-area modules still exists. Hence, there is an ongoing imperative to enhance both the functional layer and the preparation process of PSMs so as to narrow down this existing gap.

Table 2 shows the data of PSCs operated at MPPT for more than 2000 h, from which we can find that the maximum running time of the existing PSCs is 9000 h 115 . The durability of silicon solar cells significantly surpasses that of PSCs in terms of operational lifespan. What’s more, to address the substantial variations in ambient temperatures during different operational conditions (temperature, humidity, etc.), the establishment of a standardized metric becomes imperative for assessing the long-term operational stability of the device. Such a metric would serve as a pivotal reference point for its prospective industrial applications.

The cost of preparing PSM plays a crucial role in its path to industrialization. While the preparation of PSM is straightforward and comparatively less expensive than traditional silicon solar cells, continually driving down costs remains paramount for its successful industrial advancement. However, the recycling of PSCs is still necessary for sustainable development. The dismantled PSCs are classified into two groups: non-hazardous materials (including FTO glass and metal electrodes) and hazardous materials (including lead-containing compounds). The conductive substrates, obtained through thermal, mechanical, or chemical separation methods, can be reclaimed following cleansing and restoration procedures. Incorporating these reclaimed substrates into PSC production yields noteworthy reductions in material expenses, thereby enhancing economic gains. Furthermore, recycling the top electrodes in PSMs—materials like Au, Ag, Cu, Al, and Ni—offers substantial cost savings in manufacturing when contrasted with acquiring new precious metal resources. On the other hand, recycling lead-containing materials not only slashes costs but also significantly mitigates the environmental impact of lead, a subject that will be expounded upon in the following chapter. Beyond recycling in the end product, minimizing costs at the source represents a more immediate and efficacious approach. Han’s group has significantly slashed the preparation expenses for PSM by forsaking the conventional costly HTL and substituting the expensive gold electrode with an affordable carbon electrode. This unique three-layer mesoporous membrane structure exhibits substantial potential for industrial development as a device architecture 165 .

Generally, achieving industrial development for PSCs hinges on these crucial factors: minimizing scaling-up factors, extending the device’s operational lifespan, and reducing its preparation costs. In the industrialization of large-scale perovskite devices, it is crucial to factor in both cost-efficiency and environmental considerations during the manufacturing process. Achieving industrial-scale production necessitates the development of a streamlined and simpler preparation process. This approach should enable the efficient and cost-effective fabrication of high-quality perovskite devices.

Multi-scenario applications of perovskite solar cells

In recent years, the efficiency of PSCs has improved by leaps and bounds to a similar level as silicon cells. This has led to a consensus that PSCs are the most promising next-generation photovoltaic for industrialization. Moreover, PSCs are available in a wide range of fabrication techniques and device structures, which can meet the application requirements of multiple scenarios. Therefore, researchers have made a variety of attempts on the real-life applications of PSCs, including tandem solar cells 166 , 167 , 29% efficiency by enhanced hole extraction. Science 370, 1300–1309 (2020)." href="/articles/s41377-024-01461-x#ref-CR168" id="ref-link-section-d198277038e4305">168 , building-integrated PV 169 , 170 , 171 , indoor photovoltaics 172 , 173 , space applications 174 , 175 , 176 , PSC-integrated energy storage systems 177 , 178 , 179 , and PSC-driven catalytic systems 180 , 181 , 182 , 183 , 184 (Figs. 11 and 12 ). In this section, the requirements in PSC applications and the advantages of PSCs were discussed and the newest achievements that have been made were presented. Finally, we are looking ahead to the challenges and prospects of the promising PV-integrated new technologies.

Reproduced with permission from ref. 176 , 177 , 179 , 187 , 295 , 296 , 297 Copyright 2023 Springer Nature, 2022 Wiley-VCH, 2019 Elsevier Ltd, 2021 Wiley, 2014 American Association for Advancement of Science and 2021 Wiley-VCH

Building-integrated photovoltaics

The adjustable band gap of perovskite materials can meet the spectrum of different light sources; thus, PSCs can be applied outdoors, indoors, and even in space. The top and side facades of buildings have a long time and high intensity of sunlight, which is a good place to install PV devices. Building-integrated PV can turn the building structure into a generator to provide electricity for the building. However, the locations of windows and facades put additional requirements on PV devices, such as transparency, weight, shape, and color. This results in rigid Si solar cells not being suitable for the task, and PSCs, with the advantages of color tunability, substrate transparency and flexibility, and adjustable transparency, are the best candidates for building-integrated PV. The perovskite devices commonly used for building-integrated PV are semi-transparent and colored for partial light transmission. For semi-transparent PSCs, there exists a balance between PCE and average visible transmittance (AVT). Therefore, the PCE of semi-transparent PSCs is only close to 15% (AVT = 20%) which is much lower than non-transparent PSCs 185 . To improve the PCE, the use of transparent HTL or electrodes to enhance the light utilization of the device, and the improvement of the quality of perovskite to strengthen light absorption are effective strategies. Jun Hong Noh’s group reported a structure of perovskite/p-type oxide (NiO x )/n-type oxide (ITO) (Fig. 13a ) 186 . The p-type NiO x nanoparticle layer covered with perovskite served as a transparent HTL and buffer layer to avoid sputtering damage to perovskite during the deposition of transparent conductive oxides. Meanwhile, ITO was used as the top transparent electrode to maximize the light utilization capability of PSCs. Benefiting from this, the semi-transparent device obtained a PCE of 19.5%, which is even higher than the PCE of 19.2% for the non-transparent device. In addition, a semi-transparent device with AVT = 30.03% can be obtained by reducing the concentration of the perovskite precursor solution. The above structure improves the light utilization ability while ensuring the quality of perovskite, which provides a foundation for the industrial application of semi-transparent PSCs. For colorful PSCs, the colors presented by transmission and reflection can be adjusted by changing the perovskite band gap and transparent electrode thickness and by using optical nanostructures, optical microcavities, and photonic crystals. However, realizing colorful PSCs reduces the light-harvesting ability of the device and sacrifices the thickness of the perovskite layer which weakens the light-absorbing ability of perovskite. Thus, the PCE of colorful PSCs remains a barrier to industrialization. Increasing PCE with a guaranteed 25% AVT can only offset the effect of low J SC by increasing V OC and FF.

A summary of the requirements for multi-scenario applications (light color)

To summarize, researchers have made efforts to address the key challenges in building integrated PV, but this has brought about other problems at the same time. Currently, the cost of PSCs for building-integrated PV outweighs the benefits, it will take a long time to find the optimal answer to the balance between PCE and light transmittance/color.

Indoor photovoltaics

The rapidly growing Internet of Things (IoT) requires a continuous electrical power supply, which is driving the indoor application of flexible perovskite photovoltaics that meet its requirements. As PV devices are located indoors, they need to fulfill the following requirements: matching with indoor light sources, matching with IoT voltages, low toxicity, and mechanical flexibility. Bandgap tunable and high-voltage flexible perovskite devices are suitable for these requirements. Due to fewer photons received by the device, the indoor PV produces less output power 187 . At the present stage, the PCE of Cs 0.17 FA 0.83 PbI x Br 3-x indoor PV has already achieved 36.36% 188 . Reducing the defect density of perovskite with composite and interfacial engineering to suppress the leakage current and optimizing the perovskite composition to match the visible emission spectrum of the indoor light source can achieve a significant increase in PCE. Perovskite indoor photovoltaics have already met the initial requirements in efficiency, but it is the stability that is critical for sustained power generation. Compared to outdoors, light and heat are mild indoors. Therefore, the degradation mechanism of indoor PV is different from that of outdoor. It is mainly the production of a few photoelectrons that allows partial filling of the trap state thus accelerating the long-term degradation 187 . The strategies such as cation and anion combination engineering, additive engineering, anti-solvent engineering, and defect management effectively extend the lifetime of perovskite indoor PV. As shown in Fig. 13b , Min et al. 189 have attempted to use a flexible quasi-2D perovskite solar cell module for self-powering wearable biosensors that provide continuous and non-invasive metabolic monitoring. The flexible device provided sufficient power under both outdoor and indoor conditions (PCE over 31% under indoor light illumination) to maintain the biosensor working continuously for 12 h. This work confirms the feasibility of integrating PSCs with multiple indoor devices.

Despite the impressive progress that has been gained in indoor photovoltaics, there are still problems in several areas. First, the inconsistency between indoor and outdoor light sources and environments has brought about changes in the concentration of charge carriers and recombination dynamics 190 . Under indoor light source irradiation, the carrier concentration is much lower than that under solar illumination. As a result, bimolecular recombination is naturally mitigated and trap-induced recombination is amplified. The corresponding device performance is affected by the shunt resistance ( R SH ), which modulates both FF and V OC . Under solar radiation, the effect of the trap state in the films is hidden by the high charge density and bimolecular recombination dominates. The corresponding device performance is mainly affected by the series resistance ( R S ). When R S increases, FF and J SC decrease. Second, relevant measurements have to be performed to simulate real indoor conditions and to establish a common standard. In addition, the toxic effects of the perovskite devices are amplified indoors. If the above problems are solved, the development of perovskite indoor PV will even surpass that of outdoor PV.

Space application

Perovskite photovoltaics with radiation tolerance and defect tolerance have attracted attention for space applications as well. The water-free, oxygen-free, and shade-free space environment seems to mitigate the degradation of PSCs. However, the space environment brings other challenges such as particle radiation, high UV radiation, thermal cycling, and vacuum stability. In addition, space applications involve the process of being carried by space equipment, so PV devices are required to be lightweight, low-cost, and mechanically flexible. Although Si and III-V multi-junction compound solar cells (CdTe, GaAs, CIGS) are currently used for most of the space PVs, their high preparation cost, high weight, and rigid structure all lead to low energy efficiency. Therefore, suitable alternatives for Si and III-V multi-junction compound solar cells need to be found. The flexible PSCs with low cost and high specific power (i.e., power-to-weight ratio) are an ideal choice. Reb et al. 191 mounted standard PSCs based on mesoporous TiO 2 and SnO 2 on a suborbital rocket to observe device performance. The devices showed satisfactory performance (power density over 14 mW·cm −2 ) while the rocket reached the highest point of 239 kilometers for 6 minutes with temperatures ranging from 30 °C to 60 °C. This time of observation, though short, proved that PSCs have a promising future for space applications. The most significant problem faced by perovskites in space is radiation. When energetically charged particles interact with a material, they transfer and deposit their momentum and energy into the material. The irradiated material produces defects in the internal molecular structure due to ionization and atomic displacement, and the encapsulation glass also turns black. This leads to poor performance and even damage to semiconductor devices. Recently, Kirmani et al. evaporated a 1 μm thick silicon oxide layer on the top of devices that acts as a barrier layer (Fig. 13c ) 192 . It protected the device from damage blocking 0.05 MeV protons at an injection of 10 15 cm −2 . The device was even exposed to α-radiation and atomic oxygen without degradation of PCE. Meanwhile, this led to an increase in device lifetime up to 20 and 30 times in low- and high-Earth orbits, respectively. This barrier technology is a critical step for PSCs toward space applications. On August 29, 2021, the on-board PSCs were flown in low Earth orbit (LEO) outside the International Space Station (ISS) for six months during the 15th Materials ISS Experiment (MISSE-15) (Fig. 13d ) 193 . This was the first long-term flight of PSCs in LEO, further confirming that PSCs can survive in the space environment. However, the high vacuum and high-temperature characteristics of space make the stability of perovskite films challenging. Under extreme conditions, the MA-based perovskite film degrades into gaseous products, and a large number of holes are created in the perovskite film 194 . With the help of the Cs shrinking lattice, CsFAMA-based mixed cationic perovskite films show promising stability compared to MA-based perovskite 195 . Comparison and optimization of multiple perovskite materials may be an effective way to enhance stability.

Space applications of PSCs have been initially developed, but some challenges have yet to be overcome. For example, the standards for evaluating solar cells in space applications are the AIAA-S111 eligibility standard based on Si and III-V materials 196 , which are not fully suitable for perovskite; the damage mechanisms of PSCs by energetic particles and radiation are not yet clear; simulating realistic outer-space conditions is difficult; and how to design the appropriate devices and encapsulations. The PSC with unique advantages has given hope for the implementation of photovoltaics in space, which is possibly the next generation of space solar cells.

PV-integrated energy storage and fuel conversion systems

The periodic variations in the intensity of solar irradiation make it impossible for solar cells to consistently generate electricity at maximum power. In addition, solar cells need to consume power immediately from the conversion of light to electricity. In order to address the immediate and intermittent disadvantages of PV power generation, storing electrical energy in energy storage devices or converting it into easily storable clean energy with high energy density is the ideal strategy. The former is generally integrated with rechargeable batteries having high energy and power density, such as supercapacitors and lithium batteries, into PV-integrated energy storage systems. The latter commonly utilizes electrocatalytic reactions to prepare fuel compounds, for instance, the decomposition of water to prepare hydrogen and the reduction of CO 2 to hydrocarbons.

The first thing needed in integrating PV with them is to meet their operating voltages, i.e., voltage matching. In the past, lithium batteries have been attempted to be integrated with Si-based and dye-sensitized solar cells (DSSCs). However, the low voltage of their single-junction cells (less than 0.8 V) requires a tandem of several cells for integration to work, which brings cost and size issues. With the advantages of V OC over 1 V and low cost, PSCs are certainly more suitable than Si cells and DSSCs. Recently, Li et al. 197 demonstrated an indoor energy harvesting and storage system employing an all-solid-state photo-rechargeable battery. It comprises an all-inorganic CsPbI 2 Br PSM and an all-solid-state lithium-sulfur battery (Fig. 13e ). The energy conversion and storage unit exhibited an excellent overall energy conversion and storage efficiency of 11.2% and a high electrochemical storage ability of 1585.3 mAh/g under LED illumination. In addition, the device exhibited good safety and stability after a 200-h photo-charging and constant-current discharge cycle. If the stable operation time can be further increased, the photo-rechargeable battery system can be applied in more fields. Therefore, trying more efficient and stable PSCs and more severe tests, such as moisture, thermal, long-term operation, and charge/discharge cycle tests, are helpful for the photo-rechargeable battery system to move toward practical applications.

The device consisting of a PSC and a supercapacitor is called a photo-supercapacitor. Supercapacitors have the advantages of ultra-long cycle stability, fast charge/discharge, and high-power density, but integration with it requires high operation voltages. Therefore, enlarging the active area of PSCs or tandem connecting individual photo-supercapacitors is a good solution. Liu et al. 198 integrated a PSC with a supercapacitor based on a normal carbon electrode and demonstrated a tandem system based on four individual devices (with an active area of 7.5 cm 2 ). The system can quickly reach a stable output voltage of about 3.8 V and drive a light-emitting diode under 1.0 sun. Although it only sustained for a few minutes due to the degradation of PSCs, this also showed that PSC-based photo-supercapacitors have potential for applications in self-powered electronic devices and portable power sources.

The PSC-driven catalytic systems need the PV electrolyzer to provide a voltage greater than the reaction overpotential. Generally, the operating voltage for water-splitting should exceed V = 1.23 + φ HER + φ OER 199 . Similarly, for CO 2 reduction to CO, the operating voltage for CO 2 reduction should exceed V = 1.34 + η Cathode + η Anode 199 . The V OC of PSCs is generally more than 1 V so it is anticipated that only 2 PSCs in tandem can provide the required operating voltage. The fabrication of a monolithic integrated all-perovskite stacked photocathode was reported by Song et al. (Fig. 13f ) 200 . The all-perovskite tandem photocathode connected with an iridium oxide anode provided high photovoltaic voltages over 2 V at zero applied bias under AM1.5 G 1 sun illumination. Hence, the PSC-driven catalytic systems yielded a solar-to-hydrogen (STH) conversion efficiency of 15%. Moreover, it can operate continuously in water for more than 120 h under simulated 1 sun illumination with less than 5% efficiency loss. At present, PSCs-driven catalytic systems still have relatively low STHs and short lifetimes, which makes them cost-inefficient. Therefore, it is crucial to improve the STH and stability. The STH is mainly affected by PSC photovoltaic conversion efficiency and catalytic reaction rate. The supply of efficient and stable photovoltaic devices and bifunctional catalysts holds the promise of bringing efficient, durable, and cost-effective photo-hydrogen production technology. Recently, Michael Wong & Aditya D. Mohite achieved a record STH efficiency of 20.8% and 102 h of continuous operation under AM1.5 G illumination using a monolithic perovskite/Si tandem as a photovoltaic anode and IrO x -coated conductive adhesive barriers (CABs) with Pt foils as cathodes 201 . The high STH was attributed to the high PCE of about 30% of PSC and the stable catalysis for reduction and oxidation reactions by CAB/catalyst. In addition, the CAB played the role of a protective barrier for the photocathode and anode, which not only remains unaffected in the photovoltaic performance of the PSC but also provides a high device lifetime while minimizing the cost. A techno-economic analysis showed that if a sufficiently long lifetime can be achieved, it is expected to keep the levelized cost of hydrogen below $1/kg 200 . This work provides a pathway towards inexpensive solar hydrogen production.

Converting CO 2 to fuel using solar energy may assist in CO 2 reduction and even achieve CO 2 -CO-CO 2 recycling, thus weakening the greenhouse effect. However, the higher overpotential and lower solar-to-CO (STC) efficiency of the CO 2 reduction reaction compared to water-splitting makes the PV-driven reaction more challenging. In order to meet the high voltage (>2 V) requirement, an enough number of single-junction PSCs are generally connected in tandem. Schreier et al. 202 employed 3 tandem-PSCs in combination with gold oxide electrodes and IrO 2 anodes to obtain an STC > 6.5% (Fig. 13g ). This work created a good demonstration for PSCs-driven CO 2 reduction, but there was still a room for improvement in STC. Compact electrochemical cell design, large-area electrodes and perovskite films, suitable pH environment, and electrode selection were found to reduce overpotential and improve product selectivity. Huan et al. 203 combined a stack of PSCs in series and parallel with a continuous flow electrochemical cell to minimize mass transfer limitations of CO 2 and manage resistance losses. The total efficiency of solar energy conversion to hydrocarbons was 2.3%. Similarly, Esiner et al. 204 demonstrated unassisted light-driven electrochemical CO 2 reduction to CO and CH 4 with 4 series-connected PSCs (Fig. 13h ). They achieved 8.9% STC and 2% solar-to-CH 4 conversion efficiency after 7–10 h. Including H 2 production, the total solar-to-fuel conversion efficiencies for 10 h were 8.3%–9.0%.

a (i) Configuration and (ii) photograph of the semi-transparent PSC with n-i-p structure. Reproduced with permission from ref. 186 Copyright 2022 Wiley-VCH. b Illustration of the energy-autonomous wearable device that is powered under both outdoor and indoor illumination through a quasi-2D FPSC. Reproduced with permission from ref. 189 Copyright 2023 Springer Nature. c Proton straggling in an n-i-p device without (i) and with (ii) a 1-μm-thick SiO x proton barrier. Reproduced with permission from ref. 192 Copyright 2023 Springer Nature. d Schematic Overview of the rocket flight with PSCs. Reproduced with permission from ref. 193 Copyright 2020 Elsevier Ltd. e Diagram illustrating the design of an all-solid-state Li−S battery with photo-rechargeable capabilities. Reproduced with permission from ref. 197 Copyright 2022 Elsevier Ltd. f Schematic illustration of (i) the device structure of a double-junction all-perovskite tandem photocathode and (ii) the energy band diagram for water splitting. Reproduced with permission from ref. 200 Copyright 2023 American Chemical Society. g (i) Schematic of the device combining photovoltaics with an electrochemical cell and (ii) the generalized energy diagram for converting CO 2 into CO with three PSCs. Reproduced with permission from ref. 202 Copyright 2015 Springer Nature. h Diagram depicting the light-driven electrochemical apparatus designed for the conversion of CO 2 to CO. Reproduced with permission from ref. 204 Copyright 2020 Elsevier Ltd

Taken together, these results indicate that PSCs-driven CO 2 reduction reaction is still cost-inefficient as well. Therefore, electrochemical cells and efficient catalysts need to be designed based on the characteristics of CO 2 reduction reactions to improve the conversion efficiency. Moreover, the pursuit of affordable, high-performance substitutes for expensive metal electrodes could further drive cost reduction.

Sustainability issues of perovskite solar cells

PSCs represent a significant breakthrough in the field of solar technology, with notable potential for sustainable development. These novel solar cells offer high energy conversion efficiency, relatively low manufacturing costs, and a wide range of potential applications. To achieve their sustainable development, a series of key measures must be taken. Besides the demand that research and development should be more stable, long-lasting perovskite materials to extend the lifespan of the cells and reduce resource waste, continuously improving the production process of PSCs and minimizing the environmental impacts is of the utmost importance. In the production process of PSCs, pollution arises from two primary sources: lead and hazardous solvents.

Environmental issues of lead

The adverse effects of lead toxicity.

Since the photoelectric properties and thermodynamic and environmental stability of non-lead perovskites cannot be compared with lead halide perovskites at present, the heavy metal lead in perovskites is still irreplaceable 205 , 206 , 207 , 208 , 209 . However, perovskite will be degraded to lead iodide (PbI 2 ) by light, heat, and humidity in long-term operation. Hydrogen bonding of lead iodide with water makes it soluble in water, and longer rainfall times (>10 min) can even completely dissolve the perovskite film when the device is damaged 210 . To assess the extent of the environmental impact of lead in PSCs, the lead content of the device was first estimated. A typical flat-plate device has a perovskite layer thickness of about 500 nm, then the area densities of lead corresponding to MAPbI 3 , FAPbI 3 , and CsPbI 3 in it are about 0.066 mg/cm 2 , 0.067 mg/cm 2 , and 0.077 mg/cm 2 211 , 212 . Comparing with the lead content of solder required for Si solar cells that have been industrialized so far (0.61 mg/cm 2 ), the lead content of PSCs is an order of magnitude smaller. The PSCs also meet the EU legislation requirement that “homogeneous materials” contain no more than 0.1% lead by weight 213 . If the lead in the PSC module with MAPbI 3 component is dispersed into the same area of soil below, the lead content in the soil will increase by 4.0 mg/kg, which is far below the upper limit of 250 mg/kg for agricultural soil in China 211 , 214 .

The above results seem to make it easy to assume that the lead content in PSCs is low and will not cause serious consequences. However further considering the bioavailability, the problem becomes critical. Li et al. measured the uptake of Pb by plants by growing them in Pb-contaminated soil 211 . They found that the bioavailability of Pb to plants was enhanced by a factor of 10 due to the effect of organic cations on soil pH, i.e. increasing the effective Pb concentration in soil by only 10% increased the Pb content in plants by more than 100%. In particular, at 250 mg/kg of soil Pb, plants already showed blackening and decay (Fig. 14a ). To further understand the effects of lead toxicity on organisms, Babayigit et al. performed a Zebrafish embryo acute toxicity testing (ZFET) protocol which was with 85% genetic similarity to humans 215 . Figure 14b shows stereoscopic and fluorescent pictures of transgenic embryos exposed to the chemical. For normal control embryos, fluorescent signals can be found in the yolk and lens regions. When exposed to PbI 2 , the combined effect of heavy metals and their resulting pH reduction can be observed. Embryos exhibit multiple defect types, such as increased fluorescence in the trunk curvature region and dim fluorescence in the head and neck, corresponding to dorsal curvature and cerebrovascular defects, respectively. Zeng et al. directly accounted for the toxic effects of Pb on children from an e-waste disposal area 216 . By examining blood and urinary lead concentrations and microbiota and metabolites in fecal samples of children, they came to the conclusion that high blood and urinary lead levels caused by the Pb exposure group were positively correlated with a significant reduction in gut microbial diversity and significant changes in metabolites. In addition to this, Pb 2+ , due to their similarity to biologically essential ions (Ca 2+ /Fe 2+ /Zn 2+ ), occupy their binding sites, which in turn affects normal physiological processes 217 , 218 . Excessive levels of lead in the body affect the work of the hematopoietic system, inhibit the development of the nervous system, and damage the digestive system 219 , 220 , 221 . It has a significant impact on children in particular, not only hindering intellectual development but also leading to tooth decay and learning behavioral abnormalities 216 . The order of toxicity of different types of lead sources is Pb 2+ >PSC>PbI 2 = PbO 222 .

a Comparison of mint plants cultivated in two different soil conditions: control soil (left) and soil contaminated with 250 mg kg −1 Pb 2+ perovskite (right). The range lead content in the leaves, stem, and root is indicated alongside each image. Reproduced with permission from ref. 211 Copyright 2020 Springer Nature. b Stereoscopic (left) and fluorescent (right) images showing Tg (hsp70l: GFP) embryos treated with different concentrations of PbI 2 . Reproduced with permission from ref. 215 Copyright 2016 Springer Nature. c Heat map displaying various scenarios of lead exposure to analyze potential solar plant failures. It considers the percentage of lead entering the food chain (indicating the number of panels failing) and the percentage of the European Union (EU) population exposed to this lead contamination (reflecting the extent of environmental lead spread). d Evolutionary timeline of the regulation of Pb-containing products. Reproduced with permission from ref. 223 Copyright 2022 Elsevier Ltd

As noted above, the amount of Pb leakage from just one PSC device will not cause significant environmentally undesirable results. However, after a large-scale installation of PSC components, the total amount of Pb leakage will increase by orders of magnitude with the area of use. At the same time, fixed module installation locations (soil, roof, water) can result in the same place being subjected to Pb leakage for a long period of time, causing regional environmental degradation. In addition, contaminated soil and water can easily exceed the lead content of organisms, and they can enter the food cycle to further accumulate in the human body. Lead weekly intake (LWI) levels were estimated for different percentages of lead reaching the food chain (i.e., number of faulty panels) and for different percentages of the EU population exposed to lead (i.e., the extent to which the leaked lead has diffused into the environment), as shown in Fig. 14c 223 . Due to the fixed installation nature of PSCs components at specific locations, lead leaks should be regional in nature. Then even if the percentage of lead that can reach the food chain is 10 −10 , it will still exceed the FAO limit of 0.025 mg/kg. Therefore, it is important to be concerned about the heavy metal lead in calcite, stop the lead leakage, and recycle it efficiently to reduce our exposure to lead. Many lead-containing products (e.g., paint, gasoline, ammunition) were used on a large scale without concern for lead, and were eventually banned with serious consequences (Fig. 14d ). Hence, researchers have been aware of the problems posed by lead in PSCs and have adopted a number of strategies to inhibit lead leakage, adsorb lead that has leaked, and recycle and reuse lead from end-of-life devices.

Stopping lead leakage into the environment: encapsulation technology

Physical encapsulation is a common approach to improve the operational stability of PSCs, avoiding environmental erosion and enhancing the module’s impact resistance 9 . However, the general physical encapsulation only adopts a five-layer stacked structure of glass/EVA (surlyn)/PSC/EVA/glass, which can still be severely damaged under extreme conditions such as hailstorms and fires, leading to lead leakage 224 . Jiang et al. 225 first introduced epoxy resin-based polymer (ER) as encapsulation layers and compared them with common physical encapsulation methods (Fig. 15a ). They found that ER not only dramatically increased the mechanical strength of modules, but also allowed for self-healing at high temperatures (Fig. 15b ). The encapsulated PSM was damaged by a simulated standard hail impact test (FM 44787), followed by an acid rain simulation test. The test results showed that the lead leakage rate of the target group was reduced by a factor of 375 (Fig. 15c ). Therefore, suitable physical encapsulation techniques can prevent the transfer of lead to the environment. In addition, they noted that encapsulation method, weather conditions, and response time were the main factors affecting lead leakage. Lead leakage in cold weather has rarely been studied, but at this time devices are more likely to be damaged and remain in contact with snow and water for longer periods of time. Encapsulation materials suitable for cold temperatures or all extreme weather conditions should also be sought.

a Illustration depicting various encapsulation techniques. and b Illustration outlining the experimental process for quantifying the amount of toxic lead (Pb) leakage from a module subjected to a standard hail impact test (FM 44787). c The self-healing mechanism of the ER encapsulant. Reproduced with permission from ref. 225 Copyright 2019 Springer Nature. d Diagram depicting Pb-absorbing materials, with DMDP film on the front (glass) side and EDTMP-PEO film on the rear (metal electrode) side. Reproduced with permission from ref. 226 Copyright 2020 Springer Nature. e The schematic representation of applying DMDP using the doctor-blading technique onto an EVA film (top). The encapsulation of the fabricated PSC, with DMDP-laminated EVA tapes applied to both sides (top). Reproduced with permission from ref. 10 Copyright 2021 Springer Nature

In order to carefully prevent lead from leaking out after modules have been damaged, chemical encapsulation with lead-absorbing materials is the most straightforward approach. Lead-absorbing materials usually contain phosphate 10 , 226 , 227 , carboxyl 227 , and sulfonic acid 228 , 229 groups that can interact with Pb 2+ , and are coupled with encapsulation coatings with high specific surface area, such as ionogels 227 , aerogels 228 , EVA 230 , and UV resins 229 . Li et al. first reported a DMDP and EDTMP lead-trapping material containing phosphate groups and placed them on the front and back of the device, respectively (Fig. 15d ) 226 . Only 0.2 ppm of lead leakage was measured in the damaged devices even when they were soaked in water for 3 h, confirming the effectiveness of chemical encapsulation. At the same time, they proposed a universal formula for calculating lead sequestration efficiency (SQE), which became a unified method for measuring the degree of lead leakage in subsequent works. Subsequently, they further attempted to prepare transparent absorbing tapes by coating DMDP on EVA film, which obtained an SQE of 99.9% in both n-i-p and p-i-n type devices (Fig. 15e ) 10 . In order to meet the requirements of impact resistance and lead capture, Xiao et al. reported ionogels with lead chelating groups (phosphate and carboxyl groups) and self-healing characteristics (Fig. 16a ) 227 . The encapsulated devices had only minor cracks even after being run over back and forth by a car. The damaged devices also maintained an SQE of over 99.9% after 45 days of soaking in water. All of the above studies used rigid substrates to prepare the devices, while the lead concentration obtained from flexible PSCs is more than 50 times higher than that of rigid PSCs 231 . Meanwhile, flexible devices are mostly used in portable or wearable devices, and their close contact with the human body will bring more health hazards. Therefore, for flexible devices, Li et al. used flexible sulfonated graphene aerogel combined with PDMS (PDMS-SGA) for encapsulation (Fig. 16bi ) 228 . The encapsulated devices showed excellent lead capture performance, whether the damaged devices were subjected to immersion, acid rain, high-temperature tests, or the more stringent TCLP tests (Fig. 16bii ). In addition, they developed a highly acidic cation exchange resin (UVR-C) for both rigid and flexible devices (Fig. 16ci ) 229 . Utilizing the chelation of Pb 2+ by the sulfonic acid group and the rapid cation exchange reaction between Pb 2+ and Na + , UVR-C is able to capture Pb quickly. As shown in Fig. 16cii ), it has great performance in both rigid and flexible devices. In conclusion, chemical encapsulation can hinder lead leakage on the basis of mechanical strength. However, the extra cost (Fig. 16ciii ) of encapsulation cannot be ignored, and thus many researchers have turned their attention to inhibiting the lead leakage directly 229 .

a Scheme of device structures, exploration of ionogel microstructure, and lead adsorption mechanisms, alongside progressive images illustrating the degradation of perovskite films during water soaking. Reproduced with permission from ref. 227 Copyright 2021 American Association for the Advancement of Science. b (i) Illustration depicting a flexible PSM encapsulated with a combination of S-GA and PDMS on both the front side (glass) and backside (metal) (ii) Overview of the equilibrium Pb 2+ concentrations in various tests. Reproduced with permission from ref. 228 Copyright 2021 Wiley-VCH. c (i) Illustration depicting the encapsulation process involving cation-exchange resin, along with the molecular structure alterations before and after lead capture. (ii) Comparison of lead leaching between a rigid and flexible PSM using UVR and UVR-C as encapsulants. (iii) Evaluation of the cost associated with lead-adsorbing materials. Reproduced with permission from ref. 229 Copyright 2021 Elsevier Ltd

Stopping lead leakage from devices

For the convenience of comparison, the various methods and effects of preventing lead leakage were organized in Table 1 . Comparing the efficiency of physical encapsulation and chemical encapsulation (Fig. 17a ) in preventing lead leakage, it can be found that chemical encapsulation containing lead adsorption materials plays a better effect. This indicates that materials containing lead-capturing groups play a key role. As shown in Fig. 17b , the commonly used lead capturing groups can be roughly classified into five types: carbonyl 232 , 233 , carboxyl 227 , 234 , sulfhydryl 235 , 236 , 237 , 238 , sulfonic acid 228 , 229 , 239 , 240 , 241 , and phosphoric acid groups 10 , 226 , 227 , 242 . They can strongly chelate Pb 2+ and play a role in capturing or immobilizing Pb 2+ depending on the action position. If the lead-adsorbing material is resin 239 , mesoporous scaffolds 240 , MOF 238 , sponges 243 , and other high surface area materials, the lead leakage will be less. Especially for TiO 2 sponge, the physical deposition preparation method without chemical solvent is not only greener but also more suitable for large-area preparation. Recently, inspired by spider webs, Luo et al. 244 implanted a multifunctional mesoporous amino-grafted carbon web between the metal electrode and cover glass to synergistically capture lead with chemical chelation and physical adsorption. With this method, they achieved Pb sequestration efficiency exceeding 99% under extreme weather conditions. As shown in Fig. 17c , the lead-segregating material can be integrated at multiple locations in the device, e.g., at the electrode and perovskite surface, inside the electrode and perovskite, at the interface of the functional layers. However, lead-segregating functionalization at or close to the perovskite surface cannot be effective in catastrophic breakdowns. This is because they do not prevent the perovskite layer from being attacked by water through horizontally formed cracks. From the chemical decomposition perspective, perovskite is transformed in contact with water into a low-dimensional hydrated perovskite, which will be further decomposed into initial components catalyzed by water, leading to lead leakage 236 .

a Schematic showing the physical and chemical encapsulation method. b Scheme of the lead-capturing groups. c Scheme of device structures and the functional material positions. d Schematic diagram of the change and modified method of perovskite film in contact with water. e Illustration depicting the protective capacity of (DOE)PbI 4−x Cl x in preventing both inward and outward permeation. Reproduced with permission from ref. 245 Copyright 2022 Wiley-VCH. f Schematic illustration of the chemical interaction of CsPbBr 3 @HPβCD@PFOS composites and their multifaceted functions. Reproduced with permission from ref. 246 Copyright 2023 Wiley-VCH. g Schematic diagram of the lead leakage of perovskites with and without IPIE. Reproduced with permission from ref. 233 Copyright 2023 Wiley-VCH. h Diagram illustration of the control and FPD-based perovskite degradation process in water. Reproduced with permission from ref. 249 Copyright 2021 Wiley-VCH

From the perspective of dissolution behavior, due to the rapid dissolution of organic cations, the dense film transforms into a flask stacking structure (Fig. 17d ), resulting in an increase in the exposed area and dissolution rate of Pb 2+ 245 . Therefore, internal functionalization engineering of perovskite is the key to solving the lead leakage, and the main strategies were summarized into the following four (Fig. 17e–h ). The first strategy is to make perovskite water-resistant. From the perspective of modulating the dissolution behavior of Pb 2+ , Wei et al. utilized 2,2’-Dithiobis(ethylamine) cations (DOE 2+ ) to convert perovskite layers into water-resistant 2D/3D perovskites in situ 245 . The dense structure of perovskite averted collapse in water, reducing the dissolution rate of Pb 2+ . In addition, the introduction of hydrophobic molecules containing F 232 , 236 or long alkyl chains 246 is also a useful method to attenuate the impact of water erosion. The second strategy is the in-situ immobilization of Pb 2+ . By introducing molecules that strongly interact with Pb 2+ (e.g., 1,2-EDT 235 , PFDT 236 , etc.), the Pb-I bond is strengthened and the leakage of Pb 2+ is limited. In particular, Tian et al. formed a hydrophobic shell-like in situ encapsulation by mixing CsPbBr 3 @HPβCD powder, polystyrene (PS) and perfluorooctyltriethoxysilane (PFOS) 246 . The polydentate hydroxyl groups of the cyclodextrin supramolecule strongly interact with perovskite to immobilize Pb 2+ , while the superhydrophobic fluorinated silane forms strong hydrogen bonds with the cyclodextrin molecule, further enhancing the stabilization. The leakage rate of Pb 2+ ions from this complex structure is only ~3.94 ppt even after >3300 h of dynamic water flushing, which is much lower than the regulated Pb content in drinking water ( < 0.01 ppm) according to the World Health Organization guidelines. The third strategy is in-situ polymerization internal encapsulation (IPIE). In other words, polymers are formed at the grain boundaries and surfaces of perovskite using monomer molecules that can self-polymerize or cross-link at the perovskite annealing temperature 232 , 233 , 247 , 248 . The polymer network not only provides hydrophobicity similar to encapsulation but also provides multiple lead chelation sites for lead capturing or immobilization, thus effectively reducing lead leakage. The final strategy is in-situ sedimentation. PbX 2 has a high solubility constant in water ( K SP ≈ 10 −8 ). The rapid formation of low-solubility water-insoluble complexes with Pb 2+ can directly eliminate the Pb 2+ in water 241 , 249 , 250 . It is worth noting that the rate of formation of the water-insoluble complexes needs to be faster than the dissolution of PbX 2 . Endre Horváth et al. obtained a lead segregating efficiency of >99.9% using diammonium phosphate (DAP) with Pb 2+ by rapid formation of insoluble phosphates 250 . Moreover, internal functionalization engineering of perovskite in conjunction with encapsulation may bring about better lead segregating efficiency 240 , 248 . It is important to note that any lead-segregating strategy adopted should not sacrifice device performance.

Research on lead leakage from perovskite devices has been progressing, but the corresponding test methods and standards are still imperfect. Based on the test methods summarized in Table 3 , it can be seen that there is inconsistency in the area of the device tested, the method of the device is damaged and collecting dissolved Pb 2+ . Inconsistent test methods make it difficult to evaluate the extent of lead leakage. In addition, perovskite devices will be used in different scenarios and regions and then should meet different lead leakage standards. In particular, flexible devices, which are commonly used in close-to-the-body optoelectronic products, should be tested with more stringent requirements, and even require appropriate biological testing. Although the strategies discussed above can reduce lead leakage from damaged devices, they cannot prevent the irreversible decomposition of perovskite in contact with water. Fortunately, many researchers have focused on the recycling of FTO/ITO substrates 251 , 252 , 253 , metal electrodes 254 , 255 , 256 , and lead 248 , 257 , 258 , 259 from damaged devices. Realizing the recycling of damaged devices is the key to achieving cost reduction and sustainable development. In addition, the gaps between the recycling technology and the optimal recycling potential of materials, and between laboratory recycling and industrial scale-up recycling, need to be optimized. Bridging these gaps could help to reduce energy recovery times and greenhouse gas emissions. In addition, regular module recycling provides early market entry opportunities for PSCs by addressing resource shortages and relaxing initial stability 260 .

Environmental issues of toxic solvents

Solution processing technology has the advantages of simpler equipment and faster deposition speed, which is favorable for industrialized production. Therefore, most of the large-area perovskite films are prepared by it 17 , 261 . However, solution processing technology requires a large number of toxic solvents such as DMF and CB, which will hazard the environment and human health in the process of use, removal, emission, and end-of-life. As shown in Fig. 18 , Vidal et al. investigated the adverse effects of eight commonly used polar non-protonic solvents on the human body (Fig. 18a ) and the environment during the life cycle (Fig. 18b ) by the USEtox method 262 . The results showed that DMF has the highest disability-adjusted life year (DALY), i.e., the highest rate of disability, followed by DMAc. At the same time, DMF has the heaviest impact during the emission process. If the whole life cycle is considered, NMP and THF have higher energy consumption in the production process and a more serious impact on the environment. DMSO has the least hazardous effect on human health and the environment, followed by DMPU. Therefore, finding non-toxic and non-polluting solvents to partially or even completely replace hazardous solvents is a challenge for the industrialization of PSCs.

a Characterization of human health impacts presented as DALYs per kilogram of emitted substance in the context of urban air emissions. b Life cycle assessment of eight aprotic solvents for perovskite film manufacturing with four potential scenarios for EOL. Reproduced with permission from ref. 247 Copyright 2020 Springer Nature. c Diagram of rising health concerns for solvent choices in precursor dissolution. Reproduced with permission from ref. 263 Copyright 2016 Wiley-VCH

Green solvent engineering

Figure 18c illustrates the solvents commonly used in precursor solutions which were classified according to the degree of toxicity 263 . Alcohols, esters, benzenes, GBL, and acetic acid were considered non-toxic solvents, while DMF, NMP, and DMAc were severely toxic solvents. A perfect solvent for perovskite precursors not only needs to be highly soluble in the solute, but also to form a stable intermediate phase with PbI 2 for high-quality perovskite formation. In order to find a suitable precursor solvent, Gardner et al. 263 attempted to mix GBL with other nontoxic solvents (Fig. 19ai ) and evaluated them in terms of polarity, hydrogen bonding, and dispersion. Ultimately, the PSCs prepared with GBL/EtOH/AcOH obtained a PCE of 15.1%, which was still lower than the PCE of the DMF-prepared device (16.7%). However, GBL, although less toxic than DMF, is still regulated in some regions due to other factors. The safer and biodegradable γ-valerolactone (GVL) is structurally similar to GBL, and thus has been used as an alternative to GBL 264 , 265 . Recently, Miao et al. 54 reported that eco-friendly biomass-derived green solvents containing GVL and n-butyl acetate could prepare high-quality FAPbI 3 perovskites (Fig. 19aii ). A certified efficiency of 20.23% was obtained for the micro-module (12.25 cm 2 ). This is due to the stabilization of the precursor by the strong interaction between GVL and the high-valent [PbI x ] 2-x complex/FA + . Similarly, Wu et al. 266 obtained uniform, large-sized perovskite films by modulating the nucleation and crystallization growth process using low-toxicity triethyl phosphate (TEP) (Fig. 19aiii ). In addition, the new emerging ionic liquids 267 , 268 , 269 have the advantages of non-toxic, stable, easy to recycle, highly designable, and having strong interactions with Pb 2+ . Stable and viscosity-tunable perovskite inks made from methylammonium acetate (MAAc) ionic liquid solvents (Fig. 19aiv ) achieved the PCE of 20.52% and 11.80% with small-area (0.05 cm 2 ) and small-module (16.37 cm 2 ) PSCs respectively, by screen-printing technique 161 . This provides more green solvent options for industrialization of PSCs. However, considering the utilization, a minimum of 3500 L of solvent is required for a 1-GW factory, assuming a module efficiency of 15% 270 . The low-toxicity solvents mentioned above may still need to be used with considerations for hazards such as health effects from long-term exposure and explosions. Water and ethanol are considered the most environmentally friendly solvents. Preparation of perovskites from H 2 O-based precursors (Pb (NO 3 ) 2 /H 2 O 271 , PbCO 3 NFs/H 2 O 272 ) has been proven to be prospective. Ethanol-based solvent of perovskite precursors can deposit dense and homogeneous α-FAPbI 3 films without anti-solvent dripping and thus the devices obtained a high PCE (25.1%) 273 . To develop aqueous, alcohol-based perovskite precursor solutions may be the key to solving the toxic solvent problem. In addition, green solvents such as deep eutectic solvents, cyclic carbonates converting from CO 2 , and Cyrene extracted from wood chips have been used in the chemical industry field, which may be more desirable alternatives to DMF.

a (i) Photograph of inks based on decreasing vol% of GBL with equal parts alcohol/acid. Reproduced with permission from ref. 263 Copyright 2016 Wiley-VCH. (ii) Comparison of the performance for DMF: DMSO and GVL-based precursor solutions. Reproduced with permission from ref. 64 Copyright 2023 Springer Nature. (iii) Schematic of the fabrication procedures of the perovskite with TEP and (iv) MAAc. Reproduced with permission from ref. 161 , 266 Copyright Royal Society of Chemistry and 2022 Springer Nature. b (i) Chart displaying the relationship between boiling point and polarity for a selection of common solvents. (ii) Photograph of various solvents dissolving the Spiro powder and extracted perovskite films. (iii) Diagram of the CB and EA solvents for the whole PSC fabrication processing. Reproduced with permission from ref. 274 Copyright 2013 Wiley-VCH. (iv) The comparison of preparing perovskite films with CB or HAc as an anti-solvent. Reproduced with permission from ref. 276 Copyright Royal Society of Chemistry. c (i) Schematic diagram of fabrication procedures for the all-green solvent engineering approach. Reproduced with permission from ref. 278 Copyright 2022 Elsevier Ltd. (ii) Liquid–solid reaction between molten layered perovskites and MAPI. Reproduced with permission from ref. 280 Copyright 2022 Wiley-VCH. (iii) Simplified scheme presenting the sequential vacuum deposition approach. Reproduced with permission from ref. 281 Copyright 2022 American Association for Advancement of Science

Green anti-solvent engineering

The quality of perovskite films is directly affected by the nucleation growth process. Nonpolar solvents that do not destroy the perovskite structure are often employed as anti-solvents to remove excess precursor solvents and accelerate nucleation. However, commonly used anti-solvents (e.g., chlorobenzene, toluene, ether) are toxic and explosive due to their volatility and flammability. The search for a suitable green anti-solvent is equally urgent. Bu et al. summarized the polarity and boiling point of various solvents and indicated that the suitable polarity range of anti-solvents is 2.0-4.5 (Fig. 19bi, ii ). They replaced chlorobenzene with the green solvent ethyl acetate (EA), which has a polarity of 4.4, and subsequently obtained high-quality perovskite films with no pinholes and large grains (Fig. 19biii ) 274 . Recently, EA and the polymer polymethylmethacrylate were further utilized as an anti-solvent to enable NiO x -based inverse solar cells with V OC close to 1.2 V, which is due to the polymer-assisted solvent promoting the growth of perovskite crystals and passivating their interfacial and intrinsic defects 275 . Besides, the green solvent acetic acid (HAc) was also applied to replace chlorobenzene. Su et al. found that HAc not only accelerated solution nucleation but also slowed down crystal growth and inhibited the loss of organic amine salts through hydrogen bonding interactions (Fig. 19biv ) 276 . As a result, HAc-prepared tin-based perovskite solar cell devices brought about a PCE of 12.78%. In addition, they proposed that HAc congeners with no higher ability to form hydrogen bonds than HAc could be used as anti-solvents for the preparation of tin-based perovskite. What’s more, the green diethyl ether carbonate (DEC) has also been developed. The solvent-anti-solvent interaction modulated the p-type self-doping distribution in the tin-based perovskite, thereby optimizing the energy band structure. This resulted in a higher PCE of 14.2% than the CB-based device 277 . The above research progress confirms that chlorobenzene is not irreplaceable and more green anti-solvents can even improve the quality of perovskite.

All-green solvent engineering applying green solvents to both precursor and anti-solvent is a more desirable method. Cao et al. 278 successfully realized the all-green solvent treatment of perovskite films by using triethyl phosphate (TEP) as the precursor solvent and combining with low-toxicity dibutyl ether (DEE) as the anti-solvent (Fig. 19ci ). Due to the coordination of the phosphate group with Pb 2+ , a stable TEP-PbI 2 intermediate phase was formed, and finally resulted in a dense and uniform film. Recently, Jangwon Seo’s research group designed an eco-friendly solvent system (GBL + methylsulfonylmethane, MSM) suitable for the scale-up preparation and immersed in green anti-solvent (BA) to produce high-quality large-area perovskite cells 279 . The prepared perovskite solar cell devices and modules can obtain a high PCE of 24% and 21.2%, respectively. This method certainly contributes to the green development of PSCs. Solvent-free preparation of perovskite is the most desirable strategy. Mercier et al. 280 have reported that consistent melting of perovskite at moderate melting temperatures enables the preparation of layered perovskite films (Fig. 19cii ). However, this method has been demonstrated so far only in monolayer perovskites ( n = 1 of the (A) 2 (MA) n-1 Pb n I 3n+1 ). Meanwhile, melting perovskite requires more energy to reach a higher temperature (171 °C). Therefore, this method has yet to be improved and cost-evaluated. The most widespread solvent-free preparation technique is vapor phase deposition (Fig. 19ciii ) 281 . It eliminates the need for solvents and allows precise tuning of film thickness to prepare reproducible devices. However, expensive equipment, low throughput, and high energy consumption are drawbacks of this technique, which cannot be ignored. In summary, the development of an all-green solvent system is most promising for higher environmental benefits. Additionally, the green and sustainable development of PSCs will be within reach if the solvents are further recycled periodically to close the life cycle of PSCs. Sustainable cell recycling and reuse systems will help reduce waste and resource depletion, further promoting the sustainability of PSCs.

Recycling of PSCs

The fabrication of perovskite solar cells (PSCs) primarily involves the use of materials that are not only costly but also toxic. Neglecting to properly process these discarded devices can lead to both resource wastage and environmental contamination. An effective countermeasure is to maximize the recycling of materials from these devices, significantly mitigating environmental impact, reducing costs, and curtailing the lifecycle of the devices. Given that lead is the most harmful component in end-of-life devices, this section focuses on the recycling of lead from PSCs.

Recent studies have typically involved using polar solvents to dissolve the perovskite layer from end-of-life devices, resulting in a solution containing Pb 2+ . This is followed by the separation and extraction of PbI 2 using adsorbents or precipitants, preparing the way for its reuse in new devices. As shown in Fig. 20a , the end-of-life devices were dissolved in DMF to obtain a Pb-containing solution, and then the Fe-decorated hydroxyapatite (HAP/Fe) hollow composite with a negative surface charge was employed to electrostatically adsorb Pb 2+ 259 . By leveraging solubility differences, the above-mixed material was dissolved in water, and upon the addition of KI, pure PbI 2 can be obtained. The recycling yield through this method can reach 99.97%. Additionally, Pb 2+ can also be adsorbed by CER, as shown in Fig. 20b 253 . Subsequently, PbI 2 was separated and extracted by reacting with HNO 3 solution and NaI solution with a high recycling rate of 99.99%. Enabling direct precipitation of Pb 2+ for isolation and extraction is a simpler approach. As shown in Fig. 20c , Poll et al. used a deep eutectic solvent consisting of choline chloride and ethylene glycol to dissolve perovskite and separate Pb 2+ directly from the solvent by electrodeposition 282 . This method allowed for the direct extraction of 99.8% Pb from the dissolved solution of perovskite. Moreover, using NH 3 ·H 2 O as a chemical precipitant can achieve similar extraction results (Fig. 20d ) 258 . A strategy for in situ recycling of MAPbI 3 perovskite is shown in Fig. 20e 283 . They used tape to strip the Ag electrode, and HTL was dissolved in chlorobenzene. Then, the thermal degradation property of MAPbI 3 was utilized to obtain a PbI 2 layer, and the subsequent re-spin-coating of MAI solution on the PbI 2 layer could form a new perovskite film. This strategy maintained the good performance of the devices and even the re-prepared devices (14.84%) exhibited a higher PCE than the control devices (14.35%). In order to maintain or even further improve the performance of the reprepared devices, HPβCD-BTCA which can chelate Pb 2+ was employed as the passivator of perovskite and the Pb 2+ adsorbent in the dissolved solution of perovskite (Fig. 20f ) 248 . The HPβCD-BTCA@PbI 2 composites can be used directly as a recycled material for reuse, and the PCE of the as-prepared devices was as high as 20%, while the PCE of the control device was only 19.63%. Additionally, PbI 2 with a purity of 98.9% can be efficiently recovered from the HPβCD-BTCA@PbI 2 composite material.

a Illustration of the use of HAP/Fe composite for treating a Pb-containing solution pollutant and PbI 2 regaining process after Pb removal/separation. Reproduced with permission from ref. 259 Copyright 2020 Springer Nature. b Roadmap for recycling of perovskite solar modules with CER. Reproduced with permission from ref. 253 Copyright 2021 Springer Nature. c Schematic of the deep eutectic solvent-based electrochemical recycling process, showing the route to regenerate HOIP material, or feed metallic lead back into the supply chain. Reproduced with permission from ref. 282 Copyright 2016 Royal Society of Chemistry. d Illustrated cyclic utilization process of lead from carbon-based PSCs. Reproduced with permission from ref. 258 Copyright 2018 American Chemical Society. e Schematic illustration of in situ recycling PbI 2 from PVKSCs and the sequential fabrication of new solar cells. Reproduced with permission from ref. 283 Copyright 2017 Wiley-VCH. f Schematic illustration of Pb recycling and management in PSCs with HPβCD-BTCA. Reproduced with permission from ref. 248 Copyright 2023 Springer Nature

To conclude, the recycling of lead from end-of-life devices has seen pivotal advancements, leading to a high recycling yield and purity of PbI 2 . However, the recycling and reuse of other materials in discarded devices and the comprehensive recycling of devices have yet to be studied. In addition, the toxicity and cost of the organic solvents used in the preparation of the devices cannot be ignored. If the solvents are recycled regularly, the environmental hazards and costs of PSCs will be further reduced.

In this review, we discuss the main achievements, challenges, and future prospects in the industrialization of PSCs, comprising the issues of technological limitations, multi-scenario applications, and sustainable development. Currently, PSCs have made significant strides in enhancing their efficiency, yet their industrial advancement remains hampered by critical issues—stability and upscaling. Although measures like encapsulation technology can address stability concerns related to water and oxygen, challenges persist in terms of thermal and light stability. For large-area PSMs, the crucial objective is to minimize the efficiency gap between them and laboratory-scale devices. These challenges have resulted in a notable performance gap, underscoring the pressing need for further scientific breakthroughs. As for multi-scenario applications, PSCs are available in a wide range of fabrication techniques and device structures, which can meet the application requirements of multiple scenarios. With continuous exploration and optimization, PSCs are expected to be more fully utilized in more scenarios. The sustainable development of PSCs demands our utmost attention. With useful strategies such as encapsulation, green solvents, and device recycling, the environmental impact of PSCs is effectively reduced. Nonetheless, continuous improvement remains vital to ensure that these innovative solar technologies not only serve as a cornerstone of renewable energy but also embody the essence of sustainable development.

In summary, the inherent strengths of PSCs open the door to diverse applications across various environments. While notable progress has been made in enhancing their device efficiency, conquering stability, upscaling, and sustainability issues remains pivotal for their successful integration into a wide array of scenarios. Ultimately, achieving the sustainable development of PSCs is also crucial for human society. These efforts will contribute to the widespread adoption of clean energy and the role of renewable energy in the global energy transition.

Hayat, M. B., Ali, D., Monyake, K. C., Alagha, L. & Ahmed, N. Solar energy—a look into power generation, challenges, and a solar-powered future. Int. J. Energy Res. 43 , 1049–1067 (2019).

Article Google Scholar

Guney, M. S. Solar power and application methods. Renew. Sust. Energy Rev. 57 , 776–785 (2016).

Green, M. A. et al. Solar cell efficiency tables (version 51). Prog. Photovoltaics 26 , 3–12 (2018).

Lee, S.-W., Bae, S., Kim, D. & Lee, H.-S. Historical analysis of high-efficiency, large-area solar cells: toward upscaling of perovskite solar cells. Adv. Mater. 32 , 2002202 (2020).

Wehrenfennig, C., Eperon, G. E., Johnston, M. B., Snaith, H. J. & Herz, L. M. High charge carrier mobilities and lifetimes in organolead trihalide perovskites. Adv. Mater. 26 , 1584–1589, (2014).

Snaith, H. J. Perovskites: the emergence of a new era for low-cost, high-efficiency solar cells. J. Phys. Chem. Lett. 4 , 3623–3630 (2013).

Kojima, A., Teshima, K., Shirai, Y. & Miyasaka, T. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 131 , 6050–6051 (2009).

NREL. National Renewable Energy Laboratory Best ResearchCell Efficiency Chart. https://www.nrel.gov/pv/assets/pdfs/cell-pv-eff-emergingpv.pdf (NREL, 2023).

Boyd, C. C., Cheacharoen, R., Leijtens, T. & McGehee, M. D. Understanding degradation mechanisms and improving stability of perovskite photovoltaics. Chem. Rev. 119 , 3418–3451 (2019).

Li, X. et al. On-device lead-absorbing tapes for sustainable perovskite solar cells. Nat. Sustain. 4 , 1038–1041 (2021).

Li, Z. et al. Scalable fabrication of perovskite solar cells. Nat. Revi. Mater. 3 , 18017 (2018).

Article ADS Google Scholar

Li, D. et al. A review on scaling up perovskite solar cells. Adv. Funct. Mater. 31 , 2008621 (2021).

Park, N.-G. & Segawa, H. Research direction toward theoretical efficiency in perovskite solar cells. ACS Photon. 5 , 2970–2977 (2018).

Binek, A., Hanusch, F. C., Docampo, P. & Bein, T. Stabilization of the trigonal high-temperature phase of formamidinium lead iodide. J. Phys. Chem. Lett. 6 , 1249–1253, (2015).

LaMer, V. K. & Dinegar, R. H. Theory, production and mechanism of formation of monodispersed hydrosols. J. Am. Chem. Soc. 72 , 4847–4854 (1950).

Ocaña, M., Rodriguez-Clemente, R. & Serna, C. J. Uniform colloidal particles in solution: formation mechanisms. Adv. Mater. 7 , 212–216 (1995).

Chao, L. et al. Solvent engineering of the precursor solution toward large-area production of perovskite solar cells. Adv. Mater. 33 , 2005410 (2021).

Kim, G.-H. & Kim, D. S. An intermediate phase stability for high performance of perovskite solar cells. Matter 4 , 3377–3378 (2021).

Ge, Y. et al. Intermediate phase engineering with 2,2-Azodi(2-Methylbutyronitrile) for efficient and stable perovskite solar cells. Adv. Mater. 35 , 2210186 (2023).

Yang, S. et al. A key 2D intermediate phase for stable high-efficiency CsPbI 2 Br perovskite solar cells. Adv. Energy Mater. 12 , 2103019 (2022).

Li, B., Binks, D., Cao, G. & Tian, J. Engineering halide perovskite crystals through precursor chemistry. Small 15 , 1903613 (2019).

Lee, J.-W., Kim, H.-S. & Park, N.-G. Lewis acid–base adduct approach for high efficiency perovskite solar cells. Accounts Chem. Res. 49 , 311–319 (2016).

Bai, Y. et al. A pure and stable intermediate phase is key to growing aligned and vertically monolithic perovskite crystals for efficient PIN planar perovskite solar cells with high processibility and stability. Nano Energy 34 , 58–68 (2017).

McMeekin, D. P. et al. Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cells. Nat. Mater. 22 , 73–83 (2023).

Kim, J. et al. Unveiling the relationship between the perovskite precursor solution and the resulting device performance. J. Am. Chem. Soc. 142 , 6251–6260 (2020).

McMeekin, D. P. et al. Crystallization kinetics and morphology control of formamidinium–cesium mixed-cation lead mixed-halide perovskite via tunability of the colloidal precursor solution. Adv. Mater. 29 , 1607039 (2017).

Jeon, N. J. et al. Solvent engineering for high-performance inorganic–organic hybrid perovskite solar cells. Nat. Mater. 13 , 897–903 (2014).

Huang, F. et al. Gas-assisted preparation of lead iodide perovskite films consisting of a monolayer of single crystalline grains for high efficiency planar solar cells. Nano Energy 10 , 10–18 (2014).

Gotanda, T., Mori, S., Matsui, A. & Oooka, H. Effects of gas blowing condition on formation of perovskite layer on organic scaffolds. Chem. Lett. 45 , 822–824 (2016).

Chiang, C.-H. & Wu, C.-G. A method for the preparation of highly oriented MAPbI3 crystallites for high-efficiency perovskite solar cells to achieve an 86% fill factor. ACS Nano 12 , 10355–10364 (2018).

Chen, J. & Park, N.-G. Causes and solutions of recombination in perovskite solar cells. Adv. Mater. 31 , 1803019 (2019).

Yin, W.-J., Shi, T. & Yan, Y. Unusual defect physics in CH 3 NH 3 PbI 3 perovskite solar cell absorber. Appl. Phys. Lett. 104 , 063903 (2014).

Noel, N. K. et al. Enhanced photoluminescence and solar cell performance via Lewis base passivation of organic–inorganic lead halide perovskites. ACS Nano 8 , 9815–9821 (2014).

Buin, A. et al. Materials processing routes to trap-free halide perovskites. Nano Lett. 14 , 6281–6286 (2014).

Buin, A., Comin, R., Xu, J., Ip, A. H. & Sargent, E. H. Halide-dependent electronic structure of organolead perovskite materials. Chem. Mater. 27 , 4405–4412 (2015).

Wang, S. et al. Lewis acid/base approach for efficacious defect passivation in perovskite solar cells. J. Mater. Chem. A 8 , 12201–12225 (2020).

Zhang, F. et al. Suppressing defects through the synergistic effect of a Lewis base and a Lewis acid for highly efficient and stable perovskite solar cells. Energy Environ. Sci. 11 , 3480–3490 (2018).

Yang, Z. et al. Multifunctional phosphorus-containing Lewis acid and base passivation enabling efficient and moisture-stable perovskite solar cells. Adv. Funct. Mater. 30 , 1910710 (2020).

Shao, Y., Xiao, Z., Bi, C., Yuan, Y. & Huang, J. Origin and elimination of photocurrent hysteresis by fullerene passivation in CH 3 NH 3 PbI 3 planar heterojunction solar cells. Nat. Commun. 5 , 5784 (2014).

Li, Z. et al. Extrinsic ion migration in perovskite solar cells. Energy Environ. Sci. 10 , 1234–1242 (2017).

Abate, A. et al. Supramolecular halogen bond passivation of organic–inorganic halide perovskite solar cells. Nano Lett . 14 , 3247–3254 (2014).

Li, C. et al. Emerging alkali metal ion (Li + , Na + , K + and Rb + ) doped perovskite films for efficient solar cells: recent advances and prospects. J. Mater. Chem. A 7 , 24150–24163 (2019).

Zhao, W., Yao, Z., Yu, F., Yang, D. & Liu, S. Alkali metal doping for improved CH 3 NH 3 PbI 3 perovskite solar cells. Adv. Sci. 5 , 1700131 (2018).

Kausar, A. et al. Advent of alkali metal doping: a roadmap for the evolution of perovskite solar cells. Chem. Soc. Rev. 50 , 2696–2736 (2021).

Turren-Cruz, S.-H. et al. Enhanced charge carrier mobility and lifetime suppress hysteresis and improve efficiency in planar perovskite solar cells. Energy Environ. Sci. 11 , 78–86 (2018).

Meazza, L. et al. Halogen-bonding-triggered supramolecular gel formation. Nat. Chem. 5 , 42–47 (2013).

Gong, X. et al. Strong electron acceptor of a fluorine-containing group leads to high performance of perovskite solar cells. ACS Appl. Mater. Interfaces 13 , 41149–41158 (2021).

Liu, K. et al. Fullerene derivative anchored SnO 2 for high-performance perovskite solar cells. Energy Environ. Sci. 11 , 3463–3471 (2018).

Xu, J. et al. Perovskite–fullerene hybrid materials suppress hysteresis in planar diodes. Nat. Commun. 6 , 7081 (2015).

Wei, J. et al. Mechanisms and suppression of photoinduced degradation in perovskite solar cells. Adv. Energy Mater. 11 , 2002326 (2021).

Li, Y. et al. Passivation of defects in perovskite solar cell: from a chemistry point of view. Nano Energy 77 , 105237 (2020).

Lee, J.-W. et al. A bifunctional Lewis base additive for microscopic homogeneity in perovskite solar cells. Chem 3 , 290–302 (2017).

Hou, J. et al. Ethylenediamine chlorides additive assisting formation of high-quality formamidinium-caesium perovskite film with low trap density for efficient solar cells. J. Power Sources 449 , 227484 (2020).

Lee, S.-H. et al. Acid dissociation constant: a criterion for selecting passivation agents in perovskite solar cells. ACS Energy Lett . 6 , 1612–1621 (2021).

Ahn, N. et al. Trapped charge-driven degradation of perovskite solar cells. Nat. Commun. 7 , 13422 (2016).

Afroz, M. A., Garai, R., Gupta, R. K. & Iyer, P. K. Additive-assisted defect passivation for minimization of open-circuit voltage loss and improved perovskite solar cell performance. ACS Appl. Energy Mater. 4 , 10468–10476 (2021).

Jiang, X. et al. Molecular dipole engineering of carbonyl additives for efficient and stable perovskite solar cells. Angew. Chem. Int. Ed. 62 , e202302462 (2023).

Zhang, H. et al. Efficient and stable chemical passivation on perovskite surface via bidentate anchoring. Adv. Energy Mater. 9 , 1803573 (2019).

Zhou, Z., Pang, S., Liu, Z., Xu, H. & Cui, G. Interface engineering for high-performance perovskite hybrid solar cells. J. Mater. Chem. A 3 , 19205–19217 (2015).

Minemoto, T. & Murata, M. Theoretical analysis on effect of band offsets in perovskite solar cells. Sol. Energy Mat. Sol. Cells 133 , 8–14 (2015).

Yajima, T. et al. Controlling band alignments by artificial interface dipoles at perovskite heterointerfaces. Nat. Commun. 6 , 6759 (2015).

Xie, Y. et al. Facile RbBr interface modification improves perovskite solar cell efficiency. Mater. Today Chem. 14 , 100179 (2019).

Zuo, L. et al. Tailoring the interfacial chemical interaction for high-efficiency perovskite solar cells. Nano Lett . 17 , 269–275 (2017).

Duan, J. et al. Effect of side-group-regulated dipolar passivating molecules on CsPbBr 3 perovskite solar cells. ACS Energy Lett. 6 , 2336–2342 (2021).

Zhao, B. et al. Introduction of multifunctional triphenylamino derivatives at the perovskite/HTL interface to promote efficiency and stability of perovskite solar cells. ACS Appl. Mater. Interfaces 12 , 9300–9306 (2020).

Lin, R. et al. All-perovskite tandem solar cells with 3D/3D bilayer perovskite heterojunction. Nature 620 , 994–1000 (2023).

Vos, A. D. Detailed balance limit of the efficiency of tandem solar cells. J. Phys. D Appl. Phys. 13 , 839 (1980).

Liu, X. et al. Over 28% efficiency perovskite/Cu(InGa)Se 2 tandem solar cells: highly efficient sub-cells and their bandgap matching. Energy Environ. Sci. 16 , 5029–5046 (2023).

Wang, X. et al. Highly efficient perovskite/organic tandem solar cells enabled by mixed-cation surface modulation. Adv. Mater. 35 , 2305946 (2023).

Yu, W. et al. Recent advances on interface engineering of perovskite solar cells. Nano Res. 15 , 85–103 (2022).

Wang, X. et al. Reducing optical reflection loss for perovskite solar cells via printable mesoporous SiO 2 antireflection coatings. Adv. Funct. Mater. 32 , 2203872 (2022).

Chin, X. Y. et al. Interface passivation for 31.25%-efficient perovskite/silicon tandem solar cells. Science 381 , 59–63 (2023).

Tan, X. et al. Stabilizing CsPbI3 perovskite for photovoltaic applications. Matter 6 , 691–727 (2023).

Goldschmidt, V. M. Die Gesetze der krystallochemie. Naturwissenschaften 14 , 477–485 (1926).

Green, M. A., Ho-Baillie, A. & Snaith, H. J. The emergence of perovskite solar cells. Nat. Photon. 8 , 506–514 (2014).

Li, C. et al. Formability of ABX 3 (X = F, Cl, Br, I) halide perovskites. Acta Crystallogr. B 64 , 702–707 (2008).

Chatterjee, S. & Pal, A. J. Influence of metal substitution on hybrid halide perovskites: towards lead-free perovskite solar cells. J. Mater. Chem. A 6 , 3793–3823 (2018).

Li, Z. et al. Stabilizing perovskite structures by tuning tolerance factor: formation of formamidinium and cesium lead iodide solid-state alloys. Chem. Mater. 28 , 284–292 (2016).

Zhang, Y., Grancini, G., Feng, Y., Asiri, A. M. & Nazeeruddin, M. K. Optimization of stable quasi-cubic FA x MA 1–x PbI 3 perovskite structure for solar cells with efficiency beyond 20%. ACS Energy Lett. 2 , 802–806 (2017).

Sun, Q. & Yin, W.-J. Thermodynamic stability trend of cubic perovskites. J. Am. Chem. Soc. 139 , 14905–14908 (2017).

Bartel, C. J. et al. New tolerance factor to predict the stability of perovskite oxides and halides. Sci. Adv. 5 , eaav0693 (2019).

Yang, J., Siempelkamp, B. D., Liu, D. & Kelly, T. L. Investigation of CH 3 NH 3 PbI 3 degradation rates and mechanisms in controlled humidity environments using in situ techniques. ACS Nano 9 , 1955–1963, (2015).

Christians, J. A., Miranda Herrera, P. A. & Kamat, P. V. Transformation of the excited state and photovoltaic efficiency of CH 3 NH 3 PbI 3 perovskite upon controlled exposure to humidified air. J. Am. Chem. Soc. 137 , 1530–1538, (2015).

Yun, J. S. et al. Humidity-induced degradation via grain boundaries of HC(NH 2 ) 2 PbI 3 planar perovskite solar cells. Adv. Funct. Mater. 28 , 1705363 (2018).

Niu, G. et al. Study on the stability of CH 3 NH 3 PbI 3 films and the effect of post-modification by aluminum oxide in all-solid-state hybrid solar cells. J. Mater. Chem. A 2 , 705–710 (2014).

Yao, W. et al. In situ microscopic observation of humidity-induced degradation in all-inorganic perovskite films. ACS Appl. Energy Mater. 5 , 8092–8102 (2022).

Zheng, H. et al. High-performance mixed-dimensional perovskite solar cells with enhanced stability against humidity, heat and UV light. J. Mater. Chem. A 6 , 20233–20241 (2018).

Li, W. et al. Efficient and stable mesoscopic perovskite solar cell in high humidity by localized Dion-Jacobson 2D-3D heterostructures. Nano Energy 91 , 106666 (2022).

Yang, J. et al. High-performance perovskite solar cells with excellent humidity and thermo-stability via fluorinated perylenediimide. Adv. Energy Mater. 9 , 1900198 (2019).

Zhan, Y., Peng, J., Cao, C. & Cheng, Q. A biomineralization-inspired strategy of self-encapsulation for perovskite solar cells. Nano Energy 101 , 107575 (2022).

Meng, K. et al. Humidity-induced defect-healing of formamidinium-based perovskite films. Small 17 , 2104165 (2021).

Habisreutinger, S. N. et al. Carbon nanotube/polymer composites as a highly stable hole collection layer in perovskite solar cells. Nano Lett. 14 , 5561–5568 (2014).

Kim, H.-S. et al. Lead Iodide perovskite sensitized all-solid-state submicron thin film mesoscopic solar cell with efficiency exceeding 9%. Sci. Rep. 2 , 591 (2012).

Pearson, A. J. et al. Oxygen degradation in mesoporous Al 2 O 3 /CH 3 NH 3 PbI 3-x Cl x perovskite solar cells: kinetics and mechanisms. Adv. Energy Mater. 6 , 1600014 (2016).

Zhang, L. & Sit, P. H. L. Ab initio study of the role of oxygen and excess electrons in the degradation of CH 3 NH 3 PbI 3 . J. Mater. Chem. A 5 , 9042–9049 (2017).

Zhuang, J., Wang, J. & Yan, F. Review on chemical stability of lead halide perovskite solar cells. Nano-Micro Lett. 15 , 84 (2023).

Ouyang, Y. et al. Photo-oxidative degradation of methylammonium lead iodide perovskite: mechanism and protection. J. Mater. Chem. A 7 , 2275–2282 (2019).

You, J. et al. Moisture assisted perovskite film growth for high performance solar cells. Appl. Phys. Lett. 105 , 183902 (2014).

Leijtens, T. et al. Overcoming ultraviolet light instability of sensitized TiO 2 with meso-superstructured organometal tri-halide perovskite solar cells. Nat. Commun. 4 , 2885 (2013).

Shao, S. et al. Highly reproducible Sn-based hybrid perovskite solar cells with 9% efficiency. Adv. Energy Mater. 8 , 1702019 (2018).

Han, H. Oxygen makes better inorganic perovskite solar cells. Sci. Bull. 65 , 335–336 (2020).

Brenes, R. et al. Metal halide perovskite polycrystalline films exhibiting properties of single crystals. Joule 1 , 155–167 (2017).

Fang, H.-H. et al. Ultrahigh sensitivity of methylammonium lead tribromide perovskite single crystals to environmental gases. Sci. Adv. 2 , e1600534 (2016).

Liu, S.-C. et al. Investigation of oxygen passivation for high-performance all-inorganic perovskite solar cells. J. Am. Chem. Soc. 141 , 18075–18082 (2019).

Hoke, E. T. et al. Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics. Chem. Sci. 6 , 613–617 (2015).

Tsai, H. et al. Light-induced lattice expansion leads to high-efficiency perovskite solar cells. Science 360 , 67–70 (2018).

deQuilettes, D. W. et al. Photo-induced halide redistribution in organic–inorganic perovskite films. Nat. Commun. 7 , 11683 (2016).

Mosconi, E., Meggiolaro, D., Snaith, H. J., Stranks, S. D. & De Angelis, F. Light-induced annihilation of Frenkel defects in organo-lead halide perovskites. Energy Environ. Sci. 9 , 3180–3187 (2016).

Domanski, K. et al. Migration of cations induces reversible performance losses over day/night cycling in perovskite solar cells. Energy Environ. Sci. 10 , 604–613 (2017).

Abate, A. et al. Silolothiophene-linked triphenylamines as stable hole transporting materials for high efficiency perovskite solar cells. Energy Environ. Sci. 8 , 2946–2953 (2015).

Saliba, M. et al. Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency. Energy Environ. Sci. 9 , 1989–1997 (2016).

Nickel, N. H., Lang, F., Brus, V. V., Shargaieva, O. & Rappich, J. Unraveling the Light-Induced Degradation Mechanisms of CH 3 NH 3 PbI 3 Perovskite Films. Adv. Electron. Mater. 3 , 1700158 (2017).

Lepage, M. L. et al. A broadly applicable cross-linker for aliphatic polymers containing C–H bonds. Science 366 , 875–878 (2019).

Liu, K. et al. Covalent bonding strategy to enable non-volatile organic cation perovskite for highly stable and efficient solar cells. Joule 7 , 1033–1050 (2023).

Mei, A. et al. Stabilizing perovskite solar cells to IEC61215:2016 standards with over 9,000-h operational tracking. Joule 4 , 2646–2660 (2020).

Koehl, M., Heck, M., Wiesmeier, S. & Wirth, J. Modeling of the nominal operating cell temperature based on outdoor weathering. Sol. Energy Mater. Sol. Cells 95 , 1638–1646 (2011).

Conings, B. et al. Intrinsic thermal instability of methylammonium lead trihalide perovskite. Adv. Energy Mater. 5 , 1500477 (2015).

Juarez-Perez, E. J., Hawash, Z., Raga, S. R., Ono, L. K. & Qi, Y. Thermal degradation of CH 3 NH 3 PbI 3 perovskite into NH 3 and CH 3 I gases observed by coupled thermogravimetry–mass spectrometry analysis. Energy Environ. Sci. 9 , 3406–3410 (2016).

Yang, J.-H., Yin, W.-J., Park, J.-S. & Wei, S.-H. Fast self-diffusion of ions in CH 3 NH 3 PbI 3 : the interstiticaly mechanism versus vacancy-assisted mechanism. J. Mater. Chem. A 4 , 13105–13112 (2016).

Zhu, C., Gao, J., Chen, T., Guo, X. & Yang, Y. Intrinsic thermal stability of inverted perovskite solar cells based on electrochemical deposited PEDOT. J. Energy Chem. 83 , 445–453 (2023).

Aharon, S., Cohen, B. E. & Etgar, L. Hybrid lead halide iodide and lead halide bromide in efficient hole conductor free perovskite solar cell. J. Phys. Chem. C 118 , 17160–17165 (2014).

Wang, R. et al. Caffeine improves the performance and thermal stability of perovskite solar cells. Joule 3 , 1464–1477 (2019).

Cheng, L. et al. Highly thermostable and efficient formamidinium-based low-dimensional perovskite solar cells. Angew. Chem. Int. Ed. 60 , 856–864 (2021).

Fürer, S. O. et al. Naphthalene-imide self-assembled monolayers as a surface modification of ITO for improved thermal stability of perovskite solar cells. ACS Appl. Energy Mater. 6 , 667–677 (2023).

Lao, Y. et al. Efficient perovskite solar cells with enhanced thermal stability by sulfide treatment. ACS Appl. Mater. Int. 14 , 27427–27434 (2022).

Brinkmann, K. O. et al. Suppressed decomposition of organometal halide perovskites by impermeable electron-extraction layers in inverted solar cells. Nat. Commun. 8 , 13938 (2017).

Chen, W. et al. Efficient and stable large-area perovskite solar cells with inorganic charge extraction layers. Science 350 , 944–948 (2015).

Wu, Y. et al. Thermally stable MAPbI 3 perovskite solar cells with efficiency of 19.19% and area over 1 cm 2 achieved by additive engineering. Adv. Mater. 29 , 1701073 (2017).

Kim, S. et al. Relationship between ion migration and interfacial degradation of CH 3 NH 3 PbI 3 perovskite solar cells under thermal conditions. Sci. Rep. 7 , 1200 (2017).

Seo, J.-Y. et al. Novel p-dopant toward highly efficient and stable perovskite solar cells. Energy Environ. Sci. 11 , 2985–2992 (2018).

Liu, X. et al. Perovskite solar cells based on spiro-OMeTAD stabilized with an alkylthiol additive. Nat. Photon. 17 , 96–105 (2023).

Choi, K. et al. Thermally stable, planar hybrid perovskite solar cells with high efficiency. Energy Environ. Sci. 11 , 3238–3247 (2018).

Choi, K. et al. Heat dissipation effects on the stability of planar perovskite solar cells. Energy Environ. Sci. 13 , 5059–5067 (2020).

Kim, S.-G. et al. Capturing mobile lithium ions in a molecular hole transporter enhances the thermal stability of perovskite solar cells. Adv. Mater. 33 , 2007431 (2021).

Daškevičiū tė, Š. et al. Nonspiro, fluorene-based, amorphous hole transporting materials for efficient and stable perovskite solar cells. Adv. Sci. 5 , 1700811 (2018).

Liu, Z., Sun, B., Shi, T., Tang, Z. & Liao, G. Enhanced photovoltaic performance and stability of carbon counter electrode based perovskite solar cells encapsulated by PDMS. J. Mater. Chem. A 4 , 10700–10709 (2016).

Ma, S. et al. 1000 h operational lifetime perovskite solar cells by ambient melting encapsulation. Adv. Energy Mater. 10 , 1902472 (2020).

Lee, Y. I. et al. A low-temperature thin-film encapsulation for enhanced stability of a highly efficient perovskite solar cell. Adv. Energy Mater. 8 , 1701928 (2018).

Yuan, Y. et al. Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method. Nat. Commun. 5 , 3005 (2014).

Rong, Y. et al. Toward industrial-scale production of perovskite solar cells: screen printing, slot-die coating, and emerging techniques. J. Phys. Chem. Lett. 9 , 2707–2713 (2018).

Article MathSciNet Google Scholar

Xiao, Y. et al. Large-area blade-coated solar cells: advances and perspectives. Adv. Energy Mater. 11 , 2100378 (2021).

Zhong, J.-X., Wu, W.-Q., Ding, L. & Kuang, D.-B. Blade-coating perovskite films with diverse compositions for efficient photovoltaics. Energy Environ. Mater. 4 , 277–283 (2021).

Feng, W. et al. Near-stoichiometric and homogenized perovskite films for solar cells with minimized performance variation. Angew. Chem. Int. Ed. 62 , e202300265 (2023).

Razza, S. et al. Perovskite solar cells and large area modules (100 cm 2 ) based on an air flow-assisted PbI 2 blade coating deposition process. J. Power Sources 277 , 286–291 (2015).

Tait, J. G. et al. Rapid composition screening for perovskite photovoltaics via concurrently pumped ultrasonic spray coating. J. Mater. Chem. A 4 , 3792–3797 (2016).

Chou, L.-H., Chan, J. M. W. & Liu, C.-L. Progress in spray coated perovskite films for solar cell applications. Solar RRL 6 , 2101035 (2022).

Cassella, E. J. et al. Gas-assisted spray coating of perovskite solar cells incorporating sprayed self-assembled monolayers. Adv. Sci. 9 , 2104848 (2022).

Heo, J. H. et al. Efficient and stable graded CsPbI 3−x Br x perovskite solar cells and submodules by orthogonal processable spray coating. Joule 5 , 481–494 (2021).

Bu, T. et al. Lead halide–templated crystallization of methylamine-free perovskite for efficient photovoltaic modules. Science 372 , 1327–1332 (2021).

Li, J. et al. 20.8% slot-die coated MAPbI 3 perovskite solar cells by optimal DMSO-content and age of 2-ME based precursor inks. Adv. Energy Mater. 11 , 2003460 (2021).

Hwang, K. et al. Toward large scale roll-to-roll production of fully printed perovskite solar cells. Adv. Mater. 27 , 1241–1247 (2015).

Yang, Z. et al. Slot-die coating large-area formamidinium-cesium perovskite film for efficient and stable parallel solar module. Sci. Adv. 7 , eabg3749 (2021).

Le, T. S. et al. All-slot-die-coated inverted perovskite solar cells in ambient conditions with chlorine additives. Solar RRL 6 , 2100807 (2022).

Whitaker, J. B. et al. Scalable slot-die coating of high performance perovskite solar cells. Sustain. Energy Fuels 2 , 2442–2449 (2018).

Du, M. et al. Surface redox engineering of vacuum-deposited NiO x for top-performance perovskite solar cells and modules. Joule 6 , 1931–1943 (2022).

Wu, Z. et al. Natural amino acid enables scalable fabrication of high-performance flexible perovskite solar cells and modules with areas over 300 cm 2 . Small Methods 6 , 2200669 (2022).

Basaran, O. A., Gao, H. & Bhat, P. P. Nonstandard Inkjets. Annu. Rev. Fluid Mech. 45 , 85–113 (2013).

Karunakaran, S. K. et al. Recent progress in inkjet-printed solar cells. J. Mater. Chem. A 7 , 13873–13902 (2019).

Abzieher, T. et al. Electron-beam-evaporated nickel oxide hole transport layers for perovskite-based photovoltaics. Adv. Energy Mater. 9 , 1802995 (2019).

Green, M. A. et al. Solar cell efficiency tables (version 56). Prog. Photovoltaics 28 , 629–638 (2020).

Chen, C. et al. Perovskite solar cells based on screen-printed thin films. Nature 612 , 266–271 (2022).

De Rossi, F. et al. All printable perovskite solar modules with 198 cm 2 active area and over 6% efficiency. Adv. Mater. Technol. 3 , 1800156 (2018).

Chalkias, D. A., Mourtzikou, A., Katsagounos, G., Kalarakis, A. N. & Stathatos, E. Development of greener and stable inkjet-printable perovskite precursor inks for all-printed annealing-free perovskite solar mini-modules manufacturing. Small Methods 7 , 2300664 (2023).

Lin, H. et al. Silicon heterojunction solar cells with up to 26.81% efficiency achieved by electrically optimized nanocrystalline-silicon hole contact layers. Nat. Energy 8 , 789–799 (2023).

Mei, A. et al. A hole-conductor–free, fully printable mesoscopic perovskite solar cell with high stability. Science 345 , 295–298 (2014).

Gao, P., Graetzel, M. & Nazeeruddin, M. K. Organohalide lead perovskites for photovoltaic applications. Energy Environ. Sci. 7 , 2448–2463 (2014).

McMeekin, D. P. et al. A mixed-cation lead mixed-halide perovskite absorber for tandem solar cells. Science 351 , 151–155 (2016).

Al-Ashouri, A. et al. Monolithic perovskite/silicon tandem solar cell with > 29% efficiency by enhanced hole extraction. Science 370 , 1300–1309 (2020).

Li, Y., Xu, G., Cui, C. & Li, Y. Flexible and semitransparent organic solar cells. Adv. Energy Mater. 8 , 1701791 (2018).

Lin, J. et al. Thermochromic halide perovskite solar cells. Nat. Mater. 17 , 261–267 (2018).

Xue, Q., Xia, R., Brabec, C. J. & Yip, H.-L. Recent advances in semi-transparent polymer and perovskite solar cells for power generating window applications. Energy Environ. Sci. 11 , 1688–1709 (2018).

Cheng, R. et al. Tailoring triple-anion perovskite material for indoor light harvesting with restrained halide segregation and record high efficiency beyond 36%. Adv. Energy Mater. 9 , 19011980 (2019).

ADS Google Scholar

Mathews, I., Kantareddy, S. N., Buonassisi, T. & Peters, I. M. Technology and market perspective for indoor photovoltaic cells. Joule 3 , 1415–1426 (2019).

Jacobsson, T. J. et al. Exploration of the compositional space for mixed lead halogen perovskites for high efficiency solar cells. Energy Environ. Sci. 9 , 1706–1724 (2016).

Cardinaletti, I. et al. Organic and perovskite solar cells for space applications. Sol. Energy Mat. Sol. Cell 182 , 121–127 (2018).

Tu, Y. et al. Perovskite solar cells for space applications: progress and challenges. Adv. Mater. 33 , 2006545 (2021).

Xu, J., Chen, Y. & Dai, L. Efficiently photo-charging lithium-ion battery by perovskite solar cell. Nat. Commun. 6 , 8103 (2015).

Xu, X. et al. A power pack based on organometallic perovskite solar cell and supercapacitor. ACS Nano 9 , 1782–1787 (2015).

Li, C. et al. Flexible perovskite solar cell-driven photo-rechargeable lithium-ion capacitor for self-powered wearable strain sensors. Nano Energy 60 , 247–256 (2019).

Hu, C. et al. Earth-abundant carbon catalysts for renewable generation of clean energy from sunlight and water. Nano Energy 41 , 367–376 (2017).

Poli, I. et al. Graphite-protected CsPbBr 3 perovskite photoanodes functionalised with water oxidation catalyst for oxygen evolution in water. Nat. Commun. 10 , 2097 (2019).

Zhou, Q. et al. Mn 2+ and Mn 4+ red phosphors: synthesis, luminescence and applications in WLEDs. A review. J. Mater. Chem. C 6 , 2652–2671 (2018).

You, S. et al. All-inorganic perovskite/graphitic carbon nitride composites for CO 2 photoreduction into C1 compounds under low concentrations of CO 2 . Dalton Trans. 48 , 14115–14121 (2019).

Chen, P., Ong, W.-J., Shi, Z., Zhao, X. & Li, N. Pb-based halide perovskites: recent advances in photo(electro)catalytic applications and looking beyond. Adv. Funct. Mater. 30 , 1909667 (2020).

Yang, C., Liu, D., Bates, M., Barr, M. C. & Lunt, R. R. How to accurately report transparent solar cells. Joule 3 , 1803–1809 (2019).

Jeong, M. J. et al. Oxide/halide/oxide architecture for high performance semi-transparent perovskite solar cells. Adv. Energy Mater. 12 , 2200661 (2022).

Polyzoidis, C., Rogdakis, K. & Kymakis, E. Indoor perovskite photovoltaics for the internet of things-challenges and opportunities toward market uptake. Adv. Energy Mater . 11 , 2101854 (2021).

Zhang, C. et al. Br vacancy defects healed perovskite indoor photovoltaic modules with certified power conversion efficiency exceeding 36%. Adv. Sci. 9 , 2204138 (2022).

min, J. et al. An autonomous wearable biosensor powered by a perovskite solar cell. Nat. Electron. 6 , 630–641 (2023).

Chen, Z. et al. Trap state induced recombination effects on indoor organic photovoltaic cells. ACS Energy Lett. 6 , 3203–3211 (2021).

Reb, L. K. et al. Perovskite and organic solar cells on a rocket flight. Joule 4 , 1880–1892 (2020).

Kirmani, A. R. et al. Metal oxide barrier layers for terrestrial and space perovskite photovoltaics. Nat. Energy 8 , 191–202 (2023).

McMillon-Brown, L., Luther, J. M. & Peshek, T. J. What would it take to manufacture perovskite solar cells in space? ACS Energy Lett . 7 , 1040–1042 (2022).

Yang, J. et al. Unraveling photostability of mixed cation perovskite films in extreme environment. Adv. Opt. Mater. 6 , 1800262 (2018).

Xu, X. et al. Ascorbic acid as an effective antioxidant additive to enhance the efficiency and stability of Pb/Sn-based binary perovskite solar cells. Nano Energy 34 , 392–398 (2017).

In Standard: Qualification and Quality Requirements for Space Solar Cells (AIAA S-111A-2014) AIAA Standards (American Institute of Aeronautics and Astronautics, Inc., 2014).

Li, T.-T. et al. Photo-rechargeable all-solid-state lithium−sulfur batteries based on perovskite indoor photovoltaic modules. Chem. Eng. J. 455 , 140684 (2023).

Liu, Z. et al. Novel Integration of Perovskite Solar Cell and Supercapacitor Based on Carbon Electrode for Hybridizing Energy Conversion and Storage. ACS Appl. Mater. Interfaces 9 , 22361–22368 (2017).

Yang, G. et al. Perovskite solar cell powered integrated fuel conversion and energy storage devices. Adv. Mater. 35 , 2300383 (2023).

Song, Z. et al. All-perovskite tandem photoelectrodes for unassisted solar hydrogen production. ACS Energy Lett . 8 , 2611–2619 (2023).

Fehr, A. M. K. et al. Integrated halide perovskite photoelectrochemical cells with solar-driven water-splitting efficiency of 20.8%. Nat. Commun. 14 , 3797 (2023).

Schreier, M. et al. Efficient photosynthesis of carbon monoxide from CO 2 using perovskite photovoltaics. Nat. Commun. 6 , 7326 (2015).

Huan, T. N. et al. Low-cost high-efficiency system for solar-driven conversion of CO 2 to hydrocarbons. Proc. Natl Acad. Sci. USA 116 , 9735–9740 (2019).

Esiner, S., Wang, J. & Janssen, R. A. J. Light-driven electrochemical carbon dioxide reduction to carbon monoxide and methane using perovskite photovoltaics. Cell Rep. Phys. Sci. 1 , 100058 (2020).

Ke, W. & Kanatzidis, M. G. Prospects for low-toxicity lead-free perovskite solar cells. Nat. Commun. 10 , 965 (2019).

Tao, S. et al. Absolute energy level positions in tin- and lead-based halide perovskites. Nat.Commun. 10 , 2560 (2019).

Xiao, Z., Song, Z. & Yan, Y. From lead halide perovskites to lead-free metal halide perovskites and perovskite derivatives. Adv. Mater. 31 , 1803792 (2019).

Awais, M., Kirsch, R. L., Yeddu, V. & Saidaminov, M. I. Tin halide perovskites going forward: frost diagrams offer hints. ACS Mater. Lett. 3 , 299–307 (2021).

Heo, Y. J. et al. Enhancing performance and stability of tin halide perovskite light emitting diodes via coordination engineering of Lewis acid–base adducts. Adv. Funct. Mater. 31 , 2106974 (2021).

Hailegnaw, B., Kirmayer, S., Edri, E., Hodes, G. & Cahen, D. Rain on methylammonium lead iodide based perovskites: possible environmental effects of perovskite solar cells. J. Phys. Chem. Lett. 6 , 1543–1547 (2015).

Li, J. et al. Biological impact of lead from halide perovskites reveals the risk of introducing a safe threshold. Nat. Commun. 11 , 310 (2020).

Chen, C.-H., Cheng, S.-N., Cheng, L., Wang, Z.-K. & Liao, L.-S. Toxicity, leakage, and recycling of lead in perovskite photovoltaics. Adv. Energy Mater . 13 , 2204144 (2023).

European Commission . Restriction of hazardous substances in electrical and electronic equipment (RoHS) . https://environment.ec.europa.eu/topics/waste-and-recycling/rohs-directive_en (European Commission, 2017).

Technology Standards Department of State Bureau of Environmental Protection of China . Environmental quality standard for soils GB 15618-1995 . https://www-chinesestandard-net-s.lib.hust.edu.cn:443/PDF.aspx/GB15618-1995 (Technology Standards Department of State Bureau of Environmental Protection of China, 1995).

Babayigit, A. et al. Assessing the toxicity of Pb- and Sn-based perovskite solar cells in model organism Danio rerio. Sci. Rep. 6 , 18721 (2016).

Zeng, X. et al. Alterations of the gut microbiota and metabolomics in children with e-waste lead exposure. J. Hazard. Mater. 434 , 128842 (2022).

Babayigit, A., Ethirajan, A., Muller, M. & Conings, B. Toxicity of organometal halide perovskite solar cells. Nat. Mater. 15 , 247–251, (2016).

Freire, C. et al. Adipose tissue concentrations of arsenic, nickel, lead, tin, and titanium in adults from GraMo cohort in Southern Spain: an exploratory study. Sci. Total Environ. 719 , 137458 (2020).

Lukačínová, A., Rácz, O., Lovásová, E. & Ništiar, F. Effect of lifetime low dose exposure to heavy metals on selected serum proteins of Wistar rats during three subsequent generations. Ecotoxic. Environ. Safe. 74 , 1747–1755 (2011).

Czubowicz, K., Jęśko, H., Wencel, P., Lukiw, W. J. & Strosznajder, R. P. The role of ceramide and sphingosine-1-phosphate in Alzheimer’s disease and other neurodegenerative disorders. Mol. Neurobiol. 56 , 5436–5455 (2019).

Mabrouk, A. Thymoquinone attenuates lead-induced nephropathy in rats. J. Biochem. Mol. Toxicol. 33 , e22238 (2019).

Bae, S.-Y. et al. Hazard potential of perovskite solar cell technology for potential implementation of “safe-by-design” approach. Sci. Rep. 9 , 4242 (2019).

Ponti, C. et al. Environmental lead exposure from halide perovskites in solar cells. Trend. Ecol. Evol. 37 , 281–283 (2022).

Li, J. et al. Encapsulation of perovskite solar cells for enhanced stability: Structures, materials and characterization. J. Power Sources 485 , 229313 (2021).

Jiang, Y. et al. Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation. Nat. Energy 4 , 585–593 (2019).

Li, X. et al. On-device lead sequestration for perovskite solar cells. Nature 578 , 555–558 (2020).

Xiao, X. et al. Lead-adsorbing ionogel-based encapsulation for impact-resistant, stable, and lead-safe perovskite modules. Sci. Adv. 7 , eabi8249 (2021).

Li, Z. et al. Sulfonated graphene aerogels enable safe-to-use flexible perovskite solar modules. Adv. Energy Mater . 12 , 2103236 (2022).

Li, Z. et al. An effective and economical encapsulation method for trapping lead leakage in rigid and flexible perovskite photovoltaics. Nano Energy 93 , 106853 (2022).

Huang, Z. et al. Water-resistant and flexible perovskite solar cells via a glued interfacial layer. Adv. Funct. Mater. 29 , 1902629 (2019).

Moody, N. et al. Assessing the regulatory requirements of lead-based perovskite photovoltaics. Joule 4 , 970–974 (2020).

Zhang, J. et al. Thermally crosslinked F-rich polymer to inhibit lead leakage for sustainable perovskite solar cells and modules. Angew. Chem. Int. Ed. 62 , e202305221 (2023).

Tian, C. et al. In situ polymerizing internal encapsulation strategy enables stable perovskite solar cells toward lead leakage suppression. Adv. Funct. Mater. 33 , 2302270 (2023).

Zhang, Y. et al. Dual function of l-phenylalanine as a modification layer toward enhanced device performance and mitigated lead leakage in perovskite solar cells. Solar RRL 7 , 2200806 (2023).

Pei, Y. et al. Boosting near-infrared luminescence of lanthanide in Cs 2 AgBiCl 6 double perovskites via breakdown of the local site symmetry. Angew. Chem. Int. Ed. 61 , e202205276 (2022).

Zhang, H. et al. Design of superhydrophobic surfaces for stable perovskite solar cells with reducing lead leakage. Adv. Energy Mater. 11 , 2102281 (2021).

He, Z. et al. Simultaneous chemical crosslinking of SnO 2 and perovskite for high-performance planar perovskite solar cells with minimized lead leakage. Solar RRL 6 , 2200567 (2022).

Wu, S. et al. 2D metal–organic framework for stable perovskite solar cells with minimized lead leakage. Nat. Nanotechnol. 15 , 934–940 (2020).

Chen, S. et al. Trapping lead in perovskite solar modules with abundant and low-cost cation-exchange resins. Nat. Energy 5 , 1003–1011 (2020).

Chen, S. et al. Preventing lead leakage with built-in resin layers for sustainable perovskite solar cells. Nat. Sustain. 4 , 636–643 (2021).

Hu, Y. et al. Dual functions of performance improvement and lead leakage mitigation of perovskite solar cells enabled by phenylbenzimidazole sulfonic acid. Small Methods 6 , 2101257 (2022).

Meng, X. et al. A biomimetic self-shield interface for flexible perovskite solar cells with negligible lead leakage. Adv. Funct. Mater. 31 , 2106460 (2021).

Valastro, S. et al. Preventing lead leakage in perovskite solar cells with a sustainable titanium dioxide sponge. Nat. Sustain. 6 , 974–983 (2023).

Luo, H. et al. Bioinspired “cage traps” for closed-loop lead management of perovskite solar cells under real-world contamination assessment. Nat. Commun. 14 , 4730 (2023).

Wei, X. et al. Avoiding structural collapse to reduce lead leakage in perovskite photovoltaics. Angew. Chem. Int. Ed. 61 , e202204314 (2022).

Tian, T. et al. Large-area waterproof and durable perovskite luminescent textiles. Nat. Commun. 14 , 234 (2023).

Niu, B. et al. Mitigating the lead leakage of high-performance perovskite solar cells via in situ polymerized networks. ACS Energy Lett . 6 , 3443–3449 (2021).

Yang, M. et al. Reducing lead toxicity of perovskite solar cells with a built-in supramolecular complex. Nat. Sustain. 6 , 1455–1464 (2023).

Liang, Y. et al. Lead leakage preventable fullerene-porphyrin dyad for efficient and stable perovskite solar cells. Adv. Funct. Mater. 32 , 2110139 (2022).

Horváth, E. et al. Fighting health hazards in lead halide perovskite optoelectronic devices with transparent phosphate salts. ACS Appl. Mater. Interfaces 13 , 33995–34002 (2021).

Augustine, B., Remes, K., Lorite, G. S., Varghese, J. & Fabritius, T. Recycling perovskite solar cells through inexpensive quality recovery and reuse of patterned indium tin oxide and substrates from expired devices by single solvent treatment. Sol. Energy Mat. Sol. Cells 194 , 74–82 (2019).

Huang, L. et al. Efficient electron-transport layer-free planar perovskite solar cells via recycling the FTO/glass substrates from degraded devices. Sol. Energy Mat. Sol. Cells 152 , 118–124 (2016).

Chen, B. et al. Recycling lead and transparent conductors from perovskite solar modules. Nat. Commun. 12 , 5859 (2021).

Li, M.-H. et al. Robust and recyclable substrate template with an ultrathin nanoporous counter electrode for organic-hole-conductor-free monolithic perovskite solar cells. ACS Appl. Mater. Interfaces 9 , 41845–41854 (2017).

Ku, Z., Xia, X., Shen, H., Tiep, N. H. & Fan, H. J. A mesoporous nickel counter electrode for printable and reusable perovskite solar cells. Nanoscale 7 , 13363–13368 (2015).

Yang, F. et al. Recycled utilization of a nanoporous Au electrode for reduced fabrication cost of perovskite solar cells. Adv. Sci. 7 , 1902474 (2020).

Binek, A. et al. Recycling perovskite solar cells to avoid lead waste. ACS Appl. Mater. Interfaces 8 , 12881–12886 (2016).

Zhang, S. et al. Cyclic utilization of lead in carbon-based perovskite solar cells. ACS Sustain. Chem. Eng. 6 , 7558–7564 (2018).

Park, S. Y. et al. Sustainable lead management in halide perovskite solar cells. Nat. Sustain. 3 , 1044–1051 (2020).

Tian, X., Roose, B., Stranks, S. D. & You, F. Periodic module rejuvenation provides early market entry for circular all-perovskite tandem photovoltaic technologies. Energy Environ. Sci. 16 , 5551–5567 (2023).

Tan, L. et al. Combined vacuum evaporation and solution process for high-efficiency large-area perovskite solar cells with exceptional reproducibility. Adv. Mater. 35 , 2205027 (2023).

Vidal, R. et al. Assessing health and environmental impacts of solvents for producing perovskite solar cells. Nat. Sustain. 4 , 277–285 (2021).

Gardner, K. L. et al. Nonhazardous solvent systems for processing perovskite photovoltaics. Adv. Energy Mater. 6 , 1600386 (2016).

Worsley, C. et al. γ-valerolactone: a nontoxic green solvent for highly stable printed mesoporous perovskite solar cells. Energy Technol. 9 , 2100312 (2021).

Miao, Y. et al. Green solvent enabled scalable processing of perovskite solar cells with high efficiency. Nat. Sustain. 6 , 1465–1473 (2023).

Wu, X. et al. Green-solvent-processed formamidinium-based perovskite solar cells with uniform grain growth and strengthened interfacial contact via a nanostructured tin oxide layer. Mater. Horizons 10 , 122–135 (2023).

Cho, N. et al. Pure crystal orientation and anisotropic charge transport in large-area hybrid perovskite films. Nat. Commun. 7 , 13407 (2016).

Seo, J.-Y. et al. Ionic liquid control crystal growth to enhance planar perovskite solar cells efficiency. Adv. Energy Mater. 6 , 1600767 (2016).

Hui, W. et al. Stabilizing black-phase formamidinium perovskite formation at room temperature and high humidity. Science 371 , 1359–1364 (2021).

Berry, J. J. et al. Perovskite photovoltaics: the path to a printable Terawatt-scale technology. ACS Energy Lett . 2 , 2540–2544 (2017).

Cao, X. et al. Achieving environment-friendly production of CsPbBr 3 films for efficient solar cells via precursor engineering. Green Chem. 23 , 2104–2112 (2021).

Zhai, P. et al. Performance-limiting formation kinetics in green water-processed perovskite solar cells. Energy Environ. Sci. 16 , 3014–3024 (2023).

Yun, H.-S. et al. Ethanol-based green-solution processing of α-formamidinium lead triiodide perovskite layers. Nat. Energy 7 , 828–834 (2022).

Bu, T. et al. Synergic interface optimization with green solvent engineering in mixed perovskite solar cells. Adv. Energy Mater. 7 , 1700576 (2017).

Wang, Z. et al. Green antisolvent-mediators stabilize perovskites for efficient NiO x -based inverted solar cells with Voc approaching 1.2 V. Chem. Eng. J. 457 , 141204 (2023).

Su, Y. et al. Environmentally friendly anti-solvent engineering for high-efficiency tin-based perovskite solar cells. Energy Environ. Sci. 16 , 2177–2186 (2023).

Zhang, Z. et al. Green-antisolvent-regulated distribution of p-type self-doping enables tin perovskite solar cells with an efficiency of over 14%. Energy Environ. Sci. 16 , 3430–3440 (2023).

Cao, X. et al. All green solvent engineering of organic–inorganic hybrid perovskite layer for high-performance solar cells. Chem. Eng. J. 437 , 135458 (2022).

Kim, Y. Y. et al. Rationally designed eco-friendly solvent system for high-performance, large-area perovskite solar cells and modules. Adv. Sci. 10 , 2300728 (2023).

Salah, M. B. H., Mercier, N., Dabos-Seignon, S. & Botta, C. Solvent-free preparation and moderate congruent melting temperature of layered lead iodide perovskites for thin-film formation. Angew. Chem. Int. Ed. 61 , e202206665 (2022).

Li, H. et al. Sequential vacuum-evaporated perovskite solar cells with more than 24% efficiency. Sci. Adv. 8 , eabo7422 (2022).

Poll, C. G. et al. Electrochemical recycling of lead from hybrid organic–inorganic perovskites using deep eutectic solvents. Green Chem. 18 , 2946–2955 (2016).

Xu, J. et al. In situ recycle of PbI 2 as a step towards sustainable perovskite solar cells. Prog. Photovoltaics 25 , 1022–1033 (2017).

Qiu, L. et al. Hybrid chemical vapor deposition enables scalable and stable Cs-FA mixed cation perovskite solar modules with a designated area of 91.8 cm 2 approaching 10% efficiency. J. Mater. Chem. A 7 , 6920–6929 (2019).

Li, N. et al. Liquid medium annealing for fabricating durable perovskite solar cells with improved reproducibility. Science 373 , 561–567 (2021).

Zhao, X. et al. Accelerated aging of all-inorganic, interface-stabilized perovskite solar cells. Science 377 , 307–310 (2022).

Jiang, Q. et al. Surface reaction for efficient and stable inverted perovskite solar cells. Nature 611 , 278–283 (2022).

Sidhik, S. et al. Deterministic fabrication of 3D/2D perovskite bilayer stacks for durable and efficient solar cells. Science 377 , 1425–1430 (2022).

Bai, Y. et al. Initializing film homogeneity to retard phase segregation for stable perovskite solar cells. Science 378 , 747–754 (2022).

You, S. et al. Radical polymeric p-doping and grain modulation for stable, efficient perovskite solar modules. Science 379 , 288–294 (2023).

Luo, L. et al. Stabilization of 3D/2D perovskite heterostructures via inhibition of ion diffusion by cross-linked polymers for solar cells with improved performance. Nat. Energy 8 , 294–303 (2023).

Li, C. et al. Rational design of Lewis base molecules for stable and efficient inverted perovskite solar cells. Science 379 , 690–694 (2023).

Rajagopal, A., Yao, K. & Jen, A. K. Y. Toward perovskite solar cell commercialization: a perspective and research roadmap based on interfacial engineering. Adv. Mater., 30 , 1800455 (2018).

Park, M. et al. Highly reproducible large-area perovskite solar cell fabrication via continuous megasonic spray coating of CH 3 NH 3 PbI 3 . Small 15 , 1804005 (2019).

Bati, A. S. R. et al. Next-generation applications for integrated perovskite solar cells. Commun. Mater. 4 , 2 (2023).

Koh, T. M. et al. Halide perovskite solar cells for building integrated photovoltaics: transforming building façades into power generators. Adv. Mater., 34 , 2104661 (2022).

Luo, J. et al. Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts. Science 345 , 1593–1596 (2014).

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Acknowledgements

The authors acknowledge financial support from the National Natural Science Foundation of China (Grant No. 52172198, 51902117, 91733301), the Fundamental Research Funds for the Central Universities (No. 2019kfyXJJS051), the Science and Technology Department of Hubei Province (No. 2017AAA190), the 111 Project (No. B07038), and the Program for HUST Academic Frontier Youth Team (2016QYTD06).

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These authors contributed equally: Chuang Yang, Wenjing Hu

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Michael Grätzel Center for Mesoscopic Solar Cells, Wuhan National Laboratory for Optoelectronics, Key Laboratory of Materials Chemistry for Energy Conversion and Storage of Ministry of Education, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, China

Chuang Yang, Wenjing Hu, Jiale Liu, Chuanzhou Han, Qiaojiao Gao, Anyi Mei, Yinhua Zhou & Hongwei Han

Collaborative Innovation Center for Advanced Organic Chemical Materials, Co-constructed by the Province and Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan, 430062, Hubei, China

Fengwan Guo

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Yang, C., Hu, W., Liu, J. et al. Achievements, challenges, and future prospects for industrialization of perovskite solar cells. Light Sci Appl 13 , 227 (2024). https://doi.org/10.1038/s41377-024-01461-x

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3 Ways to Overcome Dungeon Master Anxiety and Fear

September 03, 2024
Posted by Luke Hart

Written by Luke Hart

Every dungeon master has experienced some amount of fear or anxiety before a game or during. I know that I sure have. For me it usually happens during convention games when I'm game mastering for folks that I don't know.

And I suspect that this fear or anxiety may be a reason that many people who are interested in being a dungeon master and think that it might be a lot of fun, never take the plunge and give it a try. And I think that is very unfortunate because not only will there always be a need for more dungeon masters, but the fact is that DMing is tons of fun--Way more fun than being a player.

Watch or listen to this article by clicking the video below.

The first thing that I want to make very clear is that I am not a licensed therapist. I am simply sharing what I have learned about overcoming anxiety in the context of running D&D games, and what I have learned experientially while dealing with some general anxiety that I have had in my life. Remember, I am just a dude with a blog, and I am no substitute for professional help, if that’s what you need.

Structured Problem Solving

The first tool that I want to share with you is something called structured problem solving. Now anxiety is often caused by feelings of powerlessness, loss of control, fear of a specific thing or situation, or just a heightened flight reflex within someone. And this tool can be used to counteract or even remove some of those sources of anxiety, in the context of running a D&D game.

The first step in structured problem solving is identifying what is causing your anxiety. If your answer is “running the game” in general, break it down into smaller more specific elements. And then you address each of these elements directly and separately from the others, seeking to establish power or control over that element.

Now that probably doesn't make a whole lot of sense quite yet, which is why we're going to go over several examples. And for our examples we're going to address the elements of running a game that I think are most likely to cause anxiety or fear.

#1 What If Scenarios

What else one cause of anxiety can be the uncertainty of what to do if your players do certain things. These are the what if scenarios. What do I do if my players leave town and travel to that other town? What do I do if my players attack that NPC? What do I do if my players don't take that quest?

Because of the freeform sandbox nature of D&D, players can pretty much do anything that they decide to do, and it's then left to the dungeon master to figure out what happens and how that works. Now the easy answer here is to simply tell you to improvise, and to try to get better at improvising. In fact, I have an entire video dedicated to tips and tricks to becoming a better improviser in your D&D games .

However, I have found that one of the best solutions to handling what if scenarios is to simply prepare more. When I have my adventure or town or whatever more fully fleshed out, I'm better able to handle what if scenarios and improvise as needed. It's not that you're literally preparing everything, because you're not. It's rather that the more you know about something, the more you are an expert on the thing, the easier it is to improvise. And of course, because you've prepped more, the chances of unexpected situations happening are reduced.

So, that's an example of how structured problem solving would work. We identify the specific element, what if scenarios, and then we brainstorm and establish solutions for that problem. Specifically, we're trying to establish solutions that reduce our anxiety or fear.

#2 Making Rules Calls

So as another example, a common source of anxiety for dungeon master’s is making rules calls. You have players looking to you as the expert on the rules, and perhaps even arguing about the rules with you. So how can we reduce anxiety there? And remember We want to establish power and a sense of control in this element.

So, for making rules calls, the first thing that you should seek to do is learn the rules. The better you know the rules, the better equipped you will be to make calls on the fly. Study the rules. Look for commonalities in the rules that identify the core principles of the games design so that you can exercise those core principles when making your own calls. Look for gaps in the rules during your study and think of hypothetical scenarios where they might apply and think about how you'd address them.

The bottom line is that the more comfortable you become with the rules and the more familiar you become with making calls in the moment, the less intimidating it will seem.

Which leads us to a sub point. The more you do a thing, and the more comfortable you become with it, the less likely you are to feel anxious about it because you know that there is nothing to fear. You will have a sense of knowledge and control in that area because you've done it so many times before and you've become good at it.

#3 Speaking in Character

This source of anxiety can easily be solved for. Just don't do it. Speaking in character and especially speaking in special voices or accents is not required at all. Many amazing game masters never speak in special voices. And I know a game master who really only has two voices that he can use. One is a high-pitched feminine voice, and the other is a low pitched gruff masculine voice. But that's all he's got. And his games are still lots of fun.

The next way to solve this is to speak in character but to not change your voice at all. That way you can carry on a conversation with the players characters without any pressure to do some fancy voice acting or something. Not that any of us are really any good at it, even though we like to think that we are. We're really all just fumbling through it and hoping that nobody ever records it on camera. LOL

Now if you do want to do special voices or accents, then the solution is to research and practice. I was once asked to do a Russian accent for a friend's Kickstarter video. So, the first thing that I did is I did some research on a Russian accent and listened to some YouTube videos explaining how to do it. Then I did a bunch of practicing. And I'm still not very good at it. But I did my best.

I also want to say that accents in your fantasy world are probably completely different than accents in our real world. So, who says that you need to speak with a Scottish accent for dwarves, or a Russian accent for vampires or whatever.

Oh, and the best way to practice in my opinion is to literally carry on a conversation with yourself in the accent. You might literally be practicing the portrayal of the NPC that will be speaking with that accent. And just have a 15-minute conversation with yourself in that accent.

#4 Handling Complex Social Situations

Now for me personally handling complex social situations is probably the most likely to induce anxiety. I'm not an anxious person although I did have a panic attack once and subsequently struggled with anxiety for about a year, though now I’m fine. However, even for me dealing with social situations such as problem players can cause a little bit of trepidation. The thing is that even people who aren't subject to heightened anxiety under normal circumstances often have issues with interpersonal conflict.

So, when conflict arises in your D&D game these are my suggestions.

First, conflict is easier to address early in the situation. The longer you let the issue continue, the more the problem player will feel safe and justified in their actions. After all, if you let them get away with a thing for months or years, why are you “suddenly” coming after them?

Next, conflict is easier dealt with as a group. This is why, I suspect, that interventions are popular. So, if you don't feel comfortable addressing a conflict one-on-one with a person, do it in the context of the group. In fact, one might argue that it is the group's responsibility to deal with problems in the group, and not just the game masters. However, the game master as the leader of the group, should take the lead.

Also, be sure that you are addressing the problem from a point of understanding. In many cases the problem player may not even realize that there is a problem, and they may not be doing it intentionally or maliciously. I recommend being kind, compassionate, firm, and direct when addressing an issue. And yes, it is possible for all of those to exist together. Don't approach the issue with anger, and don't beat around the bush.

Now, there's a lot more that I could say on this topic, but my goal here is really to just give an example. If you're looking for more help with dealing with problem players, then I have a dedicated video on the topic that you can watch right here .

The Three-Three-Three Rule

OK now I want to talk about two specific non-D&D specific tools that have worked for me to reduce anxiety. The first one is called the three-three-three rule. This tool helps you mitigate anxiety by shifting your focus away from the anxiety you're feeling in the moment and directing your focus to something else.

Step one. Identify three things that you can see. Ideally say them out loud but if you can't say them to yourself.

Step two. Identify 3 sounds that you can hear.

Step three. Move three different parts of your body.

And I'm pretty sure there are variations of this as well. The one that I have used the most is where you focus objects in the room around you and then say their colors. It's possible of course that this is a different tool that I'm confusing with this tool, but the point is that it helps.

The 4-7-8 Breathing Technique

Now this is actually my favorite anxiety reduction tool. I occasionally suffer from heart palpitations or skipped heartbeats--well according to my doctor my heart isn't actually skipping it just has a very soft beat followed by a very hard beat and it makes it seem like it's skipping; There's actually a medical term for it that I just can't remember for the life of me. But my point is that when I have these palpitations, I use this breathing technique to reduce my anxiety and get through the periods when I'm dealing with these palpitations. And let me tell you what, I suspect that having heart issues has got to be near the top of the list of things that cause anxiety, especially when it feels like your heart might be stopping.

Anyway, this is how the breathing technique works. You take a deep breath for over 4 seconds. Then you hold your breath for seven seconds. And then you exhale that breath for 8 seconds. And the trick is that you want to count the seconds in your head. There's something about slowing down your breathing that helps with anxiety, and I also think that counting the seconds helps too because it takes your mind off your anxiety and gives you something else to focus on.

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How to Write Limitations of the Study (with examples)
Common types of limitations and their ramifications include: Theoretical: limits the scope, depth, or applicability of a study. Methodological: limits the quality, quantity, or diversity of the data. Empirical: limits the representativeness, validity, or reliability of the data. Analytical: limits the accuracy, completeness, or significance of ...
Understanding Limitations in Research
Methodology limitations. Not having access to data or reliable information can impact the methods used to facilitate your research. A lack of data or reliability may limit the parameters of your study area and the extent of your exploration. Your sample size may also be affected because you won't have any direction on how big or small it ...
Limitations of the Study
If serious limitations do emerge, consult with your professor about possible ways to overcome them or how to revise your study. When discussing the limitations of your research, be sure to: ... Provide the reasons why each limitation could not be overcome using the method(s) chosen to acquire or gather the data [cite to other studies that had ...
Limitations in Research
Identify the limitations: Start by identifying the potential limitations of your research. These may include sample size, selection bias, measurement error, or other issues that could affect the validity and reliability of your findings. Be honest and objective: When describing the limitations of your research, be honest and objective.
Research Limitations: Simple Explainer With Examples
Whether you're working on a dissertation, thesis or any other type of formal academic research, remember the five most common research limitations and interpret your data while keeping them in mind. Access to Information (literature and data) Time and money. Sample size and composition. Research design and methodology.
Limitations in Medical Research: Recognition, Influence, and Warning
Shortcomings and widespread misuses of research limitation justifications make findings suspect and falsely justified in many instances. ... and how to overcome them, and how they will affect the reasonableness and assessment of possible conclusions. A named limitation represents a category with numerous components. Each factor has a unique ...
How to Present a Research Study's Limitations
How scientists present them can make a big difference. iStock, Jacob Wackerhausen. Scientists work with many different limitations. First and foremost, they navigate informational limitations, work around knowledge gaps when designing studies, formulating hypotheses, and analyzing data. They also handle technical limitations, making the most of ...
PDF How to discuss your study's limitations effectively
sentence tha. signals what you're about to discu. s. For example:"Our study had some limitations."Then, provide a concise sentence or two identifying each limitation and explaining how the limitation may have affected the quality. of the study. s findings and/or their applicability. For example:"First, owing to the rarity of the ...
Limitations of the Study
If serious limitations do emerge, consult with your professor about possible ways to overcome them or how to revise your study. When discussing the limitations of your research, be sure to: Describe each limitation in detailed but concise terms; Explain why each limitation exists; Provide the reasons why each limitation could not be overcome ...
Limited by our limitations
Limited by our limitations. Study limitations represent weaknesses within a research design that may influence outcomes and conclusions of the research. Researchers have an obligation to the academic community to present complete and honest limitations of a presented study. Too often, authors use generic descriptions to describe study limitations.
How to Present the Limitations of a Study in Research?
Writing the limitations of the research papers is often assumed to require lots of effort. However, identifying the limitations of the study can help structure the research better. Therefore, do not underestimate the importance of research study limitations. 3. Opportunity to make suggestions for further research.
What are the limitations in research and how to write them?
The ideal way is to divide your limitations section into three steps: 1. Identify the research constraints; 2. Describe in great detail how they affect your research; 3. Mention the opportunity for future investigations and give possibilities. By following this method while addressing the constraints of your research, you will be able to ...
21 Research Limitations Examples
In research, studies can have limitations such as limited scope, researcher subjectivity, and lack of available research tools. Acknowledging the limitations of your study should be seen as a strength. It demonstrates your willingness for transparency, humility, and submission to the scientific method and can bolster the integrity of the study.
Limitations of a Research Study
3. Identify your limitations of research and explain their importance. 4. Provide the necessary depth, explain their nature, and justify your study choices. 5. Write how you are suggesting that it is possible to overcome them in the future. Limitations can help structure the research study better.
Limitations of the Study
Step 1. Identify the limitation (s) of the study. This part should comprise around 10%-20% of your discussion of study limitations. The first step is to identify the particular limitation (s) that affected your study. There are many possible limitations of research that can affect your study, but you don't need to write a long review of all ...
Limitations of the Study
If serious limitations do emerge, consult with your professor about possible ways to overcome them or how to reframe your study. When discussing the limitations of your research, be sure to: ... A Note about Sample Size Limitations in Qualitative Research . Sample sizes are typically smaller in qualitative research because, as the study goes on ...
PDF How to Present Limitations and 13 Alternatives
re impressive to reviewers than ignoring them.A fourfold approach can be used when presenting limitations as outlined in the Figure 13.1: (1) describe the potential limitation, (2) describe the potential impact of the limitation on your study findings, (3) discuss alternatives and why they were not selected, and (4) describe the methods that ...
How to Identify Limitations in Research
Once you have a first draft ready, consider submitting a free sample to us for proofreading to ensure that your writing is concise and error-free and your results—despite their limitations— shine through. Whether you're a veteran researcher or a novice to the field, every study has its limitations. Here's how to identify them.
How to Write about Research Limitations Without Reducing Your Impact
Writing about your limitations without reducing your impact is a valuable skills that will help your reputation as a researcher. Areas you might have "failed," in other words, your limitations, include: Confounding factors (didn't see that coming!) Your limitations don't harm your work and reputation.
If the limitations of the study cannot be avoided, how can ...
If appropriate, you can indicate how a future study can be planned to overcome the limitations of the present one. Note that these are only general strategies: more specific advice can be given only for specific limitations. For more insights, you may refer to these resources: The why and how of presenting research limitations: A case study
7 Research Challenges (And how to overcome them)
Take your time with the planning process. "It's worth consulting other researchers, doing a pilot study to test it, before you go out spending the time, money, and energy to do the big study," Crawford says. "Because once you begin the study, you can't stop.". Challenge: Assembling a Research Team.
Scientists seek to invent a safe, reliable, and cheap battery for
The new Aqueous Battery Consortium of Stanford, SLAC, and 13 other research institutions, funded by the U.S. Department of Energy, seeks to overcome the limitations of a battery using water as its electrolyte.
Collecting and reporting adverse events in low-income settings
Constraints in the healthcare system in the Gambia such as limitations in diagnostic tools limit the specificity of diagnosis when reporting adverse events. To overcome these challenges, the Medical Research Council Unit maintains a Clinical Services Department, offering medical care and diagnostic services to study participants.
How to Stop Overthinking Your Happiness
Fortunately, our research points to a solution—and the solution is pretty simple to state, if tricky to implement: When you're experiencing something positive, don't judge yourself. How tracking happiness makes us unhappy. In earlier empirical research, we showed that intensely valuing happiness indeed seems to backfire. For example ...
Answering open questions in biology using spatial genomics and
Genomics methods have uncovered patterns in a range of biological systems, but obscure important aspects of cell behavior: the shapes, relative locations, movement, and interactions of cells in space. Spatial technologies that collect genomic or epigenomic data while preserving spatial information have begun to overcome these limitations. These new data promise a deeper understanding of the ...
Sustainability
The study aims to identify and categorise the deterrents to adopting modular construction (MC) in affordable housing (AH), revealing their interconnections, and proposing strategies to overcome them. A systematic literature review (SLR) was conducted, followed by Pareto analysis and total interpretive structural modelling (TISM). A total of 75 deterrents were identified from 46 studies ...
Achievements, challenges, and future prospects for industrialization of
This review summarized the challenges in the industrialization of perovskite solar cells (PSCs), encompassing technological limitations, multi-scenario applications, and sustainable development ...
3 Ways to Overcome Dungeon Master Anxiety and Fear
Step one. Identify three things that you can see. Ideally say them out loud but if you can't say them to yourself. Step two. Identify 3 sounds that you can hear. Step three. Move three different parts of your body. And I'm pretty sure there are variations of this as well.

How to Write Limitations of the Study (with examples)

What are limitations in research?

Why is identifying limitations important?

How to write limitations

Don’t hide your limitations

Writing limitations

Examples of common limitations

Methodology limitations

Research process limitations

Final thoughts

Ensure your structure and ideas are consistent and clearly communicated

Organizing Your Social Sciences Research Paper

Importance of...

Descriptions of Possible Limitations

Structure and Writing Style

Writing Tip

Another Writing Tip

Yet Another Writing Tip

Limitations in Research – Types, Examples and Writing Guide

Limitations in Research

Types of Limitations in Research

Sample Size Limitations

Time Limitations

Selection Bias

Confounding Variables

Measurement Error

Ethical Limitations

Examples of Limitations in Research

How to Write Limitations in Research

Purpose of Limitations in Research

When to Write Limitations in Research

Importance of Limitations in Research

Advantages of Limitations in Research

About the author

Muhammad Hassan

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Research Limitations 101 📖

Overview: Research Limitations 101

What (exactly) are “research limitations”?

Need a helping hand?

Limitation #1: Access To Information

Limitation #2: Time & Money

Limitation #3: Sample Size & Composition

Limitation #4: Methodological Limitations

Limitation #5: Researcher (In)experience

Key Takeaways

Psst… there’s more!

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How to Present a Research Study’s Limitations

Do: Be Transparent

Don't: Be Defensive

Striking the Right Balance

CPS Online Graduate Studies Research Paper (UNH Manchester Library): Limitations of the Study

Limitations of the Study

Descriptions of Possible Limitations

Structure and Writing Style

Limited by our limitations

Nikki L. Bibler Zaidi

Introduction

Goals of presenting limitations

Why some authors may fail to present limitations

A guide to presenting limitations

Describe the limitations

Study design

Data collection

Data analysis

Study results

Explain the implication(s) of each limitation

Provide potential alternative approaches and explanations

Describe steps taken to minimize each limitation

How to Present the Limitations of a Study in Research?

What are the limitations of a study

Importance of limitations of a study

Why should I include limitations of research in my paper