Annealing Engineering in the Growth of Perovskite Grains

Round 1

Reviewer 1 Report

This manuscript reviews various annealing methods employed to form organic-inorganic hybrid halide perovskite and discusses the concomitant effects in crystallisation and photovoltaic application. In general, the topic looks to have a great potential to contribute on the related field.  However, there are lack of detailed information and some discussions, which are not clear at current state and should be further improved or clarified. This referee leaves several specific comments like below.

1. In introduction, the type of perovskite should be more clarified as even in the lead-based materials, different types e.g 2D, quasi-2D, 3D exist.
2. Overall, the perovskite chemical composition should be clearly identified throughout the article as there are several types of materials, e.g. mono cation or multi-cation, mono halide or mixed halide etc. For instance, “mixed halide” line 217, figure 4 – 12, figure 13 – 16, phase transition, line 412, line 436, etc. This referee suggests the authors to revise the corresponding discussions with full description of the chemical composition in the main text as well. 
   
   
3. And it would be helpful for readers if the authors provide the corresponding device structures as many different types of architectures exist.
   
   
4. Some discussion which are not yet sufficient should be improved.
   Line 78, figure 1(b) needs “value of a scale” in the scale bar.
   Line 130, The nuclei will appear at the substrate/precursor-solution interface: This is seemingly contradictory to top-down mode for crystallization described in line 86.
   Line 134, figure 3(a) needs more detailed explanation and definition of Cs, Css, Cs Max, and Hom.
   Line 134, this referee thinks that Hom means homogenous nucleation. Then how does the model explain nucleation occurring at the interface which seems heterogenous nucleation?
   Line 215, more clear explanation for “annealing window” will be helpful for readers’ understanding and convenience.   
   Line 217, explanation on "three stages" is needed.
   Line 226, what does define the stage I and II? Or what kind of processes is performed at those stages.
   Line 380 – 381, the sentence is not clear. How does semiconducting property (P-type to N-type) alter by scanning speed? It is well known that P- or N-type is determined by dopant type but the orbital overlap as a reason explained by the authors is not sufficiently clear to this referee.
   Line 493, introduction of chemical annealing is rather too short.  
   Line 495 and 497, it means what kind of organic or inorganic solvent? Extraction of organic solvents and retarding the evaporation rate are conflicting. Extraction of organic solvents would facilitate nucleation which was agreed by the authors in solvent-solvent extraction annealing. Hence, the authors should give more clear discussion on this part if they mean a balance of two events.  
   Line 523, what does “no gain” mean?
   Line 551, figure 14(b) needs more clear discussion. What do all figures (a)-(f) under figure 14(b) tell to readers?
   Line 605, what is the reference condition?
   Line 609, what is organic material?
   
   
5. This referee suggests the authors to revise English:
   In the main text, “anneal” (line 71, 76, 85, 103, 105) should be corrected to “annealing”.
   Line 124, the authors meant “superior stability to other types”?
   Line 235, short time-high temperature? Or high temperature in a short time?
   Line 551, backscattered electron image instead of back electron scattering?
   Line 605, heat transfer rate than the reference?
   
   
6. The full terms should be described when they are first mentioned:
   Line 73, GIWAXS
   Line 78, SEM, MA
   Line 96, TAS, OD
   Line 482, PCE
   Line 483, RH
   And solvent names as well, DMF (line 424), DMSO (line 260), NMP (line 542) etc.
   
   
7. Figure 12 captions should be revised.
   
   
8. In conclusion, it will be helpful if the authors explain overall view on which in the crystallization process is important and how it is related with annealing process. For instance, fast extraction of DMF/DMSO solvent for the perovskite precursors would be helpful or not? Gradient annealing vs fast or slow annealing? So, giving the authors’ opinion on what kind of criteria in the annealing processes should be looked into and prioritized to achieve high quality of materials.
   
   
9. In conclusion, line 698, this referee would like to ask how the authors foresee environmental aspect.  
   
   
10. Some references are missing their page information. And double-numbering in reference should be corrected. 

Author Response

Dear Editor,

 

   Thank you for your letter and for the reviewers’ comments concerning my manuscript entitled “Annealing engineering in the growth of perovskite grains” (ID No: crystals-1722634). Those comments are all valuable and very helpful for revising and improving our manuscript. We have substantially revised the manuscript after reading the comments provided by the reviewers.

 

Reviewers' comments:

 

Reviewer #1:

 

1. In introduction, the type of perovskite should be more clarified as even in the lead-based materials, different types e.g 2D, quasi-2D, 3D exist.

Answers: We apologize for the uncertain writing in introduction section. We have added the information you have recommended. Once more, thanks for your help. 

 

2. Overall, the perovskite chemical composition should be clearly identified throughout the article as there are several types of materials, e.g. mono cation or multi-cation, mono halide or mixed halide etc. For instance, “mixed halide” line 217, figure 4 – 12, figure 13 – 16, phase transition, line 412, line 436, etc. This referee suggests the authors to revise the corresponding discussions with full description of the chemical composition in the main text as well.

Answers: Thank you for pointing this out, and your suggestions are valuable to improve our research. The more information about the perovskite chemical composition has been illustrated in this article.

 

3. And it would be helpful for readers if the authors provide the corresponding device structures as many different types of architectures exist.

Answers: We appreciate for your precious comments. We think the focus of annealing is on the driving crystallization of the absorbing layer, so there is not much attention has been paid to the device structure. We have added some descriptions of the device structure. 

 

4. Some discussion which are not yet sufficient should be improved.

Line 78, figure 1(b) needs “value of a scale” in the scale bar.

Line 130, The nuclei will appear at the substrate/precursor-solution interface: This is seemingly contradictory to top-down mode for crystallization described in line 86.

Line 134, figure 3(a) needs more detailed explanation and definition of Cs, Css, Cs Max, and Hom.

Line 134, this referee thinks that Hom means homogenous nucleation. Then how does the model explain nucleation occurring at the interface which seems heterogenous nucleation?

Line 215, more clear explanation for “annealing window” will be helpful for readers’ understanding and convenience.  

Line 217, explanation on "three stages" is needed.

Line 226, what does define the stage I and II? Or what kind of processes is performed at those stages.

Line 380 – 381, the sentence is not clear. How does semiconducting property (P-type to N-type) alter by scanning speed? It is well known that P- or N-type is determined by dopant type but the orbital overlap as a reason explained by the authors is not sufficiently clear to this referee.

Line 493, introduction of chemical annealing is rather too short. 

Line 495 and 497, it means what kind of organic or inorganic solvent? Extraction of organic solvents and retarding the evaporation rate are conflicting. Extraction of organic solvents would facilitate nucleation which was agreed by the authors in solvent-solvent extraction annealing. Hence, the authors should give more clear discussion on this part if they mean a balance of two events. 

Line 523, what does “no gain” mean?

Line 551, figure 14(b) needs more clear discussion. What do all figures (a)-(f) under figure 14(b) tell to readers?

Line 605, what is the reference condition?

Line 609, what is organic material?

Answers: We apologize for the not sufficient discussion in this article, we have corrected some erroneous descriptions and added some clarifications to the article. We have discussed some necessary issues in detail below.

• For the “Line 130, The nuclei will appear at the substrate/precursor-solution interface: This is seemingly contradictory to top-down mode for crystallization described in line 86.”

Answers: Thanks for your comment. First, it should be stated that there is a writing mistake here, the “the substrate/precursor-solution interface” should be written as the “the substrate and precursor-solution interface”. The interface of the precursor refers to the interface between the precursor and the gas. Crystal growth first occurs where the interface energy is low. For perovskite growth, the interface energy of the liquid-gas interface is low so the film grows from top to bottom. There is no contradiction here with the top-down growth model (doi:10.1038/s41467-018-03757-0).

 

• For the “Line 134, this referee thinks that Hom means homogenous nucleation. Then how does the model explain nucleation occurring at the interface which seems heterogenous nucleation?”

Answers: We apologize for the uncomprehensive description of the article. Although LaMer diagram has been used for homogeneous nucleation, the researchers though that it can also be employed for heterogeneous nucleation of perovskites (doi:10.1021/acs.chemrev.8b00318; doi: 10.1039/c9cs00711c).

 

• For the “Line 134, figure 3(a) needs more detailed explanation and definition of Cs, Css, Cs Max, and Hom”

Answers: Thank you very much for suggestion. We have explained them in detail in the " Growth of Perovskite " section, thank you for your suggestions.

For the “Line 215, more clear explanation for “annealing window” will be helpful for readers’ understanding and convenience.  

Line 217, explanation on "three stages" is needed.

Line 226, what does define the stage I and II? Or what kind of processes is performed at those stages.

Line 380 – 381, the sentence is not clear. How does semiconducting property (P-type to N-type) alter by scanning speed? It is well known that P- or N-type is determined by dopant type but the orbital overlap as a reason explained by the authors is not sufficiently clear to this referee.

Line 493, introduction of chemical annealing is rather too short.”

Answers: We appreciate for your precious comments. We have carefully described the missing discussion in the corresponding chapter. Your suggestions are very useful for the revision of our article.

 

• For the “Line 495 and 497, it means what kind of organic or inorganic solvent? Extraction of organic solvents and retarding the evaporation rate are conflicting. Extraction of organic solvents would facilitate nucleation which was agreed by the authors in solvent-solvent extraction annealing. Hence, the authors should give more clear discussion on this part if they mean a balance of two events.”

Answers: We appreciate for your precious comments. The extraction of organic solvents and the slowing down of the evaporation rate are the different stages of crystal growth, corresponding to nucleation and crystal growth. These two stages require different evaporation rates of the solvent. More detailed discussion of this part is given in the ''Growth of Perovskite'' chapter of the article. Your suggestion is very useful and thanks for your help.

• For the “Line 523, what does “no gain” mean”

Answers: We are very sorry for the poor English writing in the article, we have corrected this mistake in the relevant chapters.

• For the “Line 551, figure 14(b) needs more clear discussion. What do all figures (a)-(f) under figure 14(b) tell to readers? Line 605, what is the reference condition? Line 609, what is organic material?”

Answers: We greatly appreciate your suggestions, and we have supplemented the missing information in the relevant section.

 

5. This referee suggests the authors to revise English:

In the main text, “anneal” (line 71, 76, 85, 103, 105) should be corrected to “annealing”.

Line 124, the authors meant “superior stability to other types”?

Line 235, short time-high temperature? Or high temperature in a short time?

Line 551, backscattered electron image instead of back electron scattering?

Line 605, heat transfer rate than the reference?

Answers: We appreciate for your precious comments. We have carefully revised the English writing, and added some necessary descriptions. Thank you for your help.

 

6. The full terms should be described when they are first mentioned:

Line 73, GIWAXS

Line 78, SEM, MA

Line 96, TAS, OD

Line 482, PCE

Line 483, RH

And solvent names as well, DMF (line 424), DMSO (line 260), NMP (line 542) etc.

Answers: We feel sorry for incorrect writing. We have comprehensively added descriptions of full terms, thank you for your help.

 

7. Figure 12 captions should be revised

Answers: Thank you for this suggestion. We have revised the caption in Figure 12.

 

8. In conclusion, it will be helpful if the authors explain overall view on which in the crystallization process is important and how it is related with annealing process. For instance, fast extraction of DMF/DMSO solvent for the perovskite precursors would be helpful or not? Gradient annealing vs fast or slow annealing? So, giving the authors’ opinion on what kind of criteria in the annealing processes should be looked into and prioritized to achieve high quality of materials.

Answers: We appreciate for your precious suggestions, which is very useful for us to revise the article. We have added a discussion about the crystallization process and the relationship between crystallization and thermal annealing in the article. We also have given some advice on how to improve crystal quality during annealing.

 

9. In conclusion, line 698, this referee would like to ask how the authors foresee environmental aspect.

Answers: We greatly appreciate your comments, we have added the effect of the environment during annealing in the solvent-solvent extraction annealing section, and explained the significance of a stable environment for the preparation of highly reproducible films.

 

10. Some references are missing their page information. And double-numbering in reference should be corrected.

Answers: We greatly appreciate your corrections, we have supplemented and revised information in some the references.

Once again, thanks for your help to processing our submission.

 

On behalf of all authors

Dr. Huachao ZAI.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper reviews different annealing methods applied to manufacture perovskite solar cells (PSCs), on the examples of lead-based perovskites mainly. Moreover, the principles of various annealing methods are present and detailed influences of annealing methods on films are discussed. Then, the comparative consideration of the differences between the various annealing methods is provided and the future technological trends in the commercial manufacture of PSCs are proposed.

To regret, the paper has very significant omissions:

1. English should be improved.
2. (Line 156) It should be no dG, but dG = 0 at α = 0.
3. (Line 162) It should be no H_m, but V_m.
4. (Lines 146 – 179) Are all equations are presented in the model [47]? Here, real references must be pointed.
5. (Lines 184 – 186) What is taken place in the range between of πΔT* and 4πΔT* ?
6. (Lines 196 – 197) The same question exists to the presented formulae that for Lines 184 – 186.
7. Very small inscriptions are present in Fig. 4.
8. (Line 229) What it is mean “hexagonal poly”?
9. (Lines 247, 293) It should be no um, but μm
10. Bad quality of Figs. 8 and 10(a).
11. Numerous abbreviations into all text are not described. For example, MAI (Line 420) and DMF/DMSO (Line 424).
12. There are broken phrases into text, for example (Lines 474 – 475).
13. The caption under 16(b) is inconsent to the figure. Where do the J-V curves and XRD spectra?
14. (Line 701) Strange text.
15. There are repeat numerations in the REFERENCES list, different fonts, absence of doi for all publications.

Author Response

Dear Editor,

 

   Thank you for your letter and for the reviewers’ comments concerning my manuscript entitled “Annealing engineering in the growth of perovskite grains” (ID No: crystals-1722634). Those comments are all valuable and very helpful for revising and improving our manuscript. We have substantially revised the manuscript after reading the comments provided by the reviewers.

 

Reviewers' comments:

 

Reviewer #2:

 

1. English should be improved

Answers: We appreciate for your precious comments. We have carefully revised the English description, thank you for your help. 

 

2. (Line 156) It should be no dG, but dG= 0 at α= 0.

Answers: We are very sorry for our incorrect writing. We have promptly corrected our mistakes.

 

3. (Line 162) It should be no H_m, but V_m.

Answers: I apologize for the incorrect writing in my discussion. We have revised our mistakes.

 

4. (Lines 146 – 179) Are all equations are presented in the model [47]? Here, real references must be pointed

Answers: Thank you for your comments. Due to the limitation of the number of pages of the article, we did not list all the formulas when describing the model, only the most important formulas were mentioned. And references have also been cited for other formulas.

 

5. (Lines 184 – 186) What is taken place in the range between of πΔT* and 4πΔT* ?

Answers: I feel sorry for incorrect writing. We have corrected the erroneous description.

 

6. (Lines 196 – 197) The same question exists to the presented formulae that for Lines 184 – 186

Answers: Thank you for your advice. Like the above formula, only the most important formula is mentioned here. And we have cited new references to the formulas in this article.

 

7. Very small inscriptions are present in Fig. 4

Answers: Thank you for pointing this out. We have replaced the pictures in time.

 

8. (Line 229) What it is mean “hexagonal poly”?

Answers: We are very sorry for this spelling error. The correct spelling is hexagonal polytypes. The hexagonal polytypes the crystalline phase for mix-ion perovskites during the annealing.

 

9. (Lines 247, 293) It should be no um, but μm

Answers: We apologize for the mistake. We have corrected the wrong information.

 

10. Bad quality of Figs. 8 and 10(a)

Answers: Thank you for pointing this out. We have replaced the pictures in time.

 

11. Numerous abbreviations into all text are not described. For example, MAI (Line 420) and DMF/DMSO (Line 424).

Answers: I feel sorry for incorrect writing. We have comprehensively added descriptions of full terms, thank you for your help.

 

12. There are broken phrases into text, for example (Lines 474 – 475).

Answers: We apologize for the bad English writing. We have corrected writing mistakes in the article.

 

13. The caption under 16(b) is inconsent to the figure. Where do the J-V curves and XRD spectra?

Answers: We apologize for the mistake in 16(b). We have revised this description of the caption in time.

 

14. (Line 701) Strange text

Answers: We sorry for the bad English writing.

 

15. There are repeat numerations in the REFERENCES list, different fonts, absence of doi for all publications.

Answers: We greatly appreciate your corrections, we have supplemented and revised information in some the references.

 

Once again, thanks for your help to processing our submission.

 

Sincerely,

 

On behalf of all authors

Dr. Huachao ZAI.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

This referee do believe that the questions provoked in the 1st round of review have been well addressed. Hence, this referee believes that it is publishable at this current form. 

Author Response

It is a great honor to receive your approval of this work.

Reviewer 2 Report

The authors have improved their paper, thank you very much. However, several points are remained non-understable and incorrect:

1.      Numerous abbreviations into all text are remained non-described, for example, into Lines 100 – 101.

2.      It is non-understable the phrase “so the time t₁- t₂ of the second phase..” (Line 145)

3.      Again, the references for formulae (1) – (8) are absent.

4.      (Lines 202 – 204). How do situations differ before and after 4pDT*? If the situation is the same, why do you consider a point 4pDT*?

5.      The proposition in Lines 201 – 203 does not correspond to the proposition in Lines 214 – 216.

6.      You should very carefully check beginning all propositions searching errors.

Author Response

Please see the attachment

Author Response File: Author Response.docx