Properties of FAPbI₃-Based Alloy Perovskite Thin Films and Their Application in Solar Cells

Round 1

Reviewer 1 Report (New Reviewer)

1- The results reported in the abstract are clear and specific, which is good. However, it would be helpful to provide some additional context about the significance of these results.

2- Avoid long  sentences 

3- provide some context for the term "tolerance factor" and explain its relevance to perovskite materials

4- While the world record efficiency of PSCs is mentioned, it would be useful to provide more information on the efficiency range of PSCs and how they compare to other photovoltaic technologies.

5- It is not clear why the perovskite precursor solutions were left to mix for 12 hours. 

6- Authors mentioned that chlorobenzene (CB) was dropped onto the perovskite/PEDOT: PSS/ITO/glass sample during the last 3 seconds of the spin-coating perovskite precursor, but they did not mention the amount of CB used. Including this information would provide more clarity.

7- Provide more information on the blade-coating technique, such as its advantages over the spin-coating method and the conditions under which it was used in this study.

8- It is mentioned that the PSCs were measured without encapsulation to evaluate their thermal/chemical stabilities, but it would be useful to provide more details on the test conditions, such as the temperature and humidity levels.

9- Provide more information on the calibration procedures used for the light intensity measurements, such as the specific reference cell used and the uncertainty in the intensity measurements (unclear).

10- Provide some additional information on the SEM imaging conditions, such as the magnification used and the type of detector employed.

11- Please explain more clearly how the absorbance spectra are related to the film quality and device performance, and how the PL measurements provide insight into the carrier lifetime and recombination processes.

12-the meaning of "segregation activation energy" and its relevance to the properties of the CsxFA1-xPbI3 films is not explained in sufficient detail, provide more context 

13- It would be helpful to provide some recommendations for future research based on the findings of this study.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report (New Reviewer)

The authors studied Surface morphologies, light harvesting abilities, crystal structures, and excitonic 13 properties of the formamiminium lead triiodide (FAPbI3) based alloy perovksite thin films by using the scanning electron microscopic images, absorbance spectra, X-ray diffraction patterns, photoluminescence (PL) spectra and time-resolved PL decaying curves, and Fabricate perovskite solar cells. However, there is nothing novel about this study, and very common measurements and low quality figures. Therefore, I would not recommend publishing it in the current version.

1. What is X in each CsxFA1-xPbI3, RbxFA1-xPbI3, and FAPb(SCNxI1-x)3?

2. Why RbxFA1-xPbI3, and FAPb(SCNxI1-x)3 PSCs under ambient atmosphere showed so poor long-term stability?

3. There are two CsxFA1-xPbI3 in Figure 5, should be changed.

4. Should add the EQE to confirm the Jsc.

Minor editing of English language required

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report (New Reviewer)

Authors gave a good response to the notes mentioned earlier 

Author Response

We thank the reviewer for reviewing our revised manuscript.

Reviewer 2 Report (New Reviewer)

The authors had addressed my concerns, but the manuscript needs to be modified before acceptance, such as the reference format, number superscript, or subscript.

pay attention to tense.

Author Response

We thank the reviewer to giving us the opportunity to correct our manuscript. The revisions are highlighted in the red words of the 2nd revised manuscript.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Please refer attachment.

Comments for author File: Comments.docx

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript focuses on the development of mixed cation formamidinium-based perovskite solar cells (PSCs), demonstrating the high performance and stability of CsFAPbI₃ perovskite material for this application. In my opinion, the novelty of the present work and the significance to the field are poor in order for this paper to be published in the Journal “Processes”. Additionally, there are sections of the investigation that need further clarification and the presentation needs major improvement/revision. Overall, I think that the present work should not be considered for publication in the Journal “Processes”. The following comments should be considered.

·         The main drawback of this work is that it does not introduce something new in the field in order to attract the readership of the Journal. Even from the fabrication (processing) point of view, the methods presented herein have already been published by other research groups in previous years. The performance of solar cell devices is also not high, considering that it is a conventional inverted structure.

·         The significance to the field is not provided by the present abstract.

·         The introduction part does not provide a comprehensive state-of-the-art on the topic, demonstrating the scientific gap and the novelty of the work.

·         The experimental part is fundamental for the reproducibility of the experiments and should be clearly presented in case there are no references for the readers’ benefit. Which was the drying temperature of the hole-transport-material? Which was the active area of the solar cells? Which were the scan rate and scan direction used to record the current-voltage curves? Which was the excitation wavelength used for the PL measurements?

·         It is not clear how the authors calculated the absorbance of the perovskite layer in “%” units.

·         The equation used to fit the experimental TRPL data should be presented.

·         The authors should define all peaks presented in the XRD patterns.

·         The hysteretic behavior is important to be studied in PSCs technology since it gives important information about both the performance and stability of the devices.

·         More in-depth discussion and experimental evidence are needed to support the main results of the present work. In the present case, the scientific background needs improvement.

·         Reading the conclusions part, it is also not clear which is the new information that the present work brings to the field.

·         Abbreviations should be defined at first mentioned in the abstract and in the main text, and used thereafter.

·         The table presenting the main photovoltaic characteristics is pinned in the conclusions part. Please revise.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript represents a study of perovskite solar cells based on mixed cation (Cs+, Rb+) or anion (SCN-) lead halide perovskite FAPbI₃. The motivation is to obtain stable PSCs, which is important for the technology implementation and cost-efficiency. Undoubtedly, the topic is very important and demanded, however there are some concerns about the manuscript the authors should address:

1. The Introduction part fails to provide a picture of how doping perovskites enhances their performance and/or stability. There are numerous reports of the effect of Cs+, Rb+, or SCN- ions on lead halide perovskites, including those cited in the manuscript, however they are mentioned in such a brief and general manner that a reader cannot apprehend what state of the art is now and what novelty the manuscript brings.

2. Lines 81-83 read: 1 mmol PbI2 and 0.9 mmol FAI were respectively mixed with 0.1 M CsI, RbI, or Pb(SCN)2 in 1 mL anhydrous DMF/DMSO (7:3; v/v) for 12 h, which formed three perovskite precursor solutions.

The choice of these ratios is not reasoned properly. It is understandable in case of Cs+: it has been reported multiple times that 15% additive of Cs improves stability of FAPbI3, so the given 10% in the manuscript looks close to the established optimal concentration. Whereas, in case of Rb+ this recipe looks less reasonable, as there have been reports that only little concentration of Rb+ improves the perovskites, larger additives causing performance degradation (doi:10.3390/nano12010157 or doi:10.1016/j.solener.2019.06.006). 

3. Even less reasonable seems the recipe with lead thiocyanate as it is to substitute PbI₂, not FAI. According to the stoichiometry, you should have obtained 0.9 mol of FAPbI₃(SCN)_3-x and a 0.2 mol surplus of lead iodide/thiocyanate. No wonder there is such a peak of PbI₂ at Fig.3. I consider this as a serious flaw in the experiment planning and interpretation. Yet, there was reported that lead thiocyanate additives can considerably improve the stability of perovskites being applied in a different manner: doi:10.1002/cssc.201601027 or doi:10.1038/ncomms11105.

Thus, in my opinion, the manuscript lacks of novelty, does not provide reasonable design of experiment, the level of discussion and conclusions is not deep enough. I suggest that the paper has to be improved considerably in order to be published in Processes. 

Minor corrections:

Spaces are missing throughout the text

Lines 41-42. It is not clear from the text that the cubic phase is preferable for PSCs

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors made an effort to improve their manuscript, and some of my comments have been addressed satisfactorily. However, I stay strong in my opinion that the novelty and significance to the field that the present work introduces are poor to be published in the Journal “Processes”. This is a main drawback for the present work to attract the readership of the Journal.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

I appreciate the authors’ attention to my comments, I can see that a lot of work has been done in order to improve the manuscript. However, unfortunately, the authors failed to address the most important concerns: the introduction does not provide sufficient background, the reasoning of the studied compositions is not provided, and the novelty and contribution of the whole study to the field is poor. I am sorry that I cannot recommend this manuscript for publishing in Processes.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf