Evaluation of SnS:Cu Thin Film Properties Obtained by USP Technique to Implement It as an Absorbent Layer in Solar Cells Using SCAPS
, Michel Rivero 2, Lizbeth Salgado-Conrado 3, Rodrigo Loera-Palomo 4, Bernardo Reyes-Durán 1 and Jorge Narro-Ríos 5Round 1
Reviewer 1 Report
The paper reposts on SnS:Cu thin films properties prepared by ultrasonic spray pyrolysis for application in solar cells. SnS and doped SnS materials are widely investigated for such applications. Some of the results (optical and electrical properties) presented in the paper were already published [21] as it was also mentioned in the introduction. The main purpose of the paper is to compare the properties of SnS:Cu films in dependence on Cu concentration from 0 % to 10 %. The problem I see is that the thickness of the films is not equal, it varies from 150 nm to 42 nm, for Cu content of 0 % to 10 %, respectively. This makes quite difficult to follow clearly the dependence on Cu concentration because the properties depend strongly on thickness too. Why the films of similar thicknesses were not prepared and discussed then?
I recommend major revision of the paper. My questions are:
Line:36 … semiconductors ig IV-VI group … ?
Line:160 … concentration causes a decrease in the peak 2θ = 26.5° …
What do you mean by a decrease in the peak? Peak intensity?
Line:220 … for the imagen analyzes … ?
Line:238 – 250 I guess this paragraph should be place in the Experimental part.
Figure 6. was already presented in [21]. The reference must be included.
I am not sure that band gap values (Eg) where derived correctly. Looking at Figure 6 a, it is obvious that absorption edge is between wavelengths of 300 and 500 nm. However estimated Eg for SnS and SnS:Cu (2%) are only 1.72 eV and 1.82 eV, respectively.
Line:276-277 … From figure 6(a), an abrupt change in the absorption edge to higher wavelengths is observed in the sample at y = 0% (undopped) with respect to Cu-doped films. …
I can observe the opposite effect in Figure 6a – the shift of the absorption edge to lower wavelengths.
Could you comment these discrepancies?
You should consider in equation (4) also reflectivity that cannot be neglected in absorption coefficient calculation because its value is 10 – 35% as you previously reported [21].
Figure 7. plots exactly the data published in Table II. in [21]. The reference must be inserted.
Line:285 … at the interval @ > 400 nm … ?
Line:358 … Sns … ? Superscript should be also used for cm2, cm3 in the table.
Line:401 … to Imagens of SEM …?
Author Response
Comments and Suggestions for Authors
The paper reposts on SnS:Cu thin films properties prepared by ultrasonic spray pyrolysis for application in solar cells. SnS and doped SnS materials are widely investigated for such applications. Some of the results (optical and electrical properties) presented in the paper were already published [21] as it was also mentioned in the introduction. The main purpose of the paper is to compare the properties of SnS:Cu films in dependence on Cu concentration from 0 % to 10 %. The problem I see is that the thickness of the films is not equal, it varies from 150 nm to 42 nm, for Cu content of 0 % to 10 %, respectively. This makes quite difficult to follow clearly the dependence on Cu concentration because the properties depend strongly on thickness too. Why the films of similar thicknesses were not prepared and discussed then?
The thin films were prepared experimentally by the USP technique through a time-limited research stay. We made a great effort to control all deposit conditions for all samples. With this in mind, the factors related to the technique such as the working temperature (370 °C), molarity in the preparation of precursor solutions (0.1M), carrier gas flow (1.0 l/min), and deposit time (1 hour) were kept constant in order to vary doping concentration. However, parameters like growth rate got out of our control, resulting in different values of thicknesses. Nevertheless, In figure 9 (Thickness effect in the absorbent layer SnS:Cu) we try to point out the relevance of this parameter inside the solar cell.
We are searching for other opportunities to use a lab where we might make SnS:Cu depositions by USP that can control not only the growth rates but other conditions too.
I recommend a major revision of the paper. My questions are:
Line:36 … semiconductors ig IV-VI group … ?
Line 37. “semiconductors ig IV-VI group” was changed to ---> “semiconductors belonging to the IV-VI group of the periodic table”
Line:160 … concentration causes a decrease in the peak 2θ = 26.5° …
What do you mean by a decrease in the peak? Peak intensity?
We refer indeed to the intensity of the peak located at that angle.
Line 199. “decrease in the peak 2θ = 26.5°” was changed to ---> “decrease in the peak intensity located in 2θ = 26.5°.”
Line:220 … for the imagen analyzes … ?
Error Corrected:
line 259. Imagen analyzes --->Image analysis
Line:238 – 250 I guess this paragraph should be placed in the Experimental part.
Line 135-148. The paragraph was moved to the experimental part (section 2.3 Image Analysis)
Figure 6. was already presented in [21]. The reference must be included.
Due to some modifications by other revisors reference [21] (doi:10.1109/pvsc.2018.8548268) is now reference [22]
Line 307. Reference Included
Figure 6. Reference Included
I am not sure that band gap values (Eg) where derived correctly. Looking at Figure 6 a, it is obvious that absorption edge is between wavelengths of 300 and 500 nm. However estimated Eg for SnS and SnS:Cu (2%) are only 1.72 eV and 1.82 eV, respectively.
We use the same Tauc method for allowed indirect optical transitions in all samples with the purpose of not involucrate another variant and we observed that defined curves were obtained. Our criterion to adjust the better bandgap was to profile the material (SnS: Cu) as an absorbent layer that could better adapt conventional Eg values reported in the literature.
Line:276-277 … From figure 6(a), an abrupt change in the absorption edge to higher wavelengths is observed in the sample at y = 0% (undopped) with respect to Cu-doped films. …
I can observe the opposite effect in Figure 6a – the shift of the absorption edge to lower wavelengths.
Could you comment these discrepancies?
We wanted to note the difference between the transmittances of the doped and undoped samples. Our mistake was writing it the other way around. This error is already corrected, thank you.
Line 317. higher wavelengths ---> lower wavelengths
You should consider in equation (4) also reflectivity that cannot be neglected in absorption coefficient calculation because its value is 10 – 35% as you previously reported [21].
The reflectance has been considered and added to equation 4. In the same way, the reflectance spectra have been added in figure 6 (b). it's worth mentioning that the optical results are actually considering reflectance.
Figure 7. plots exactly the data published in Table II. in [21]. The reference must be inserted.
Line 359. Reference Included
Figure 7. Reference Included
Line:285 … at the interval @ > 400 nm … ?
The sign that we wanted to put in place of the "@" is actually a lambda “λ”. I don't know if there was an error while sending the file. We erased and type again the symbol, we hope this doesn’t repeat.
Line 326. @ > 400 nm ---> λ > 400 nm
Line:358 … Sns … ? Superscript should be also used for cm2, cm3 in the table.
Error Corrected:
line 369. Sns --->SnS
line 399. (Table 5) cm2 and cm3 ---> cm2 and cm3
Line:401 … to Imagens of SEM …?
Error Corrected:
line 448. Imagens ---> Images
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors report an experimental study on the properties of SnS:Cu, thin films, with potential application in the development of Solar Cell. Also some simulation data are reported.
The concept of the study is of interest for the solid state readership. My major concern relies on the numerical study. I have the feeling that the simulation data are partially connected with the experimental one. Details on the numerical computations are missed and it is not quite obvious how these are related with the experiment.
For example, it is stated (line 350) that: It is worth mentioning that the parameters were optimized, how these properties were optimized and why ?
A few misprints were found, e.g line 365 Sns absorbent layer-> SnS
line 363 300-K -> 300K,
line 383 um ?
Lines 387-389, the following sentence is unclear: Figure 9 shows how efficiency then starts to increase with the increase in Cu-doped Sns 387thin layers thickness because this thicker layer will absorb more photons and generate 388more electron–hole pairs
Line 348 "The properties of the other layers are based on the parameters reported by Mimbashi et al., while in line 351, Minbashi et. al.
Author Response
Comments and Suggestions for Authors
The authors report an experimental study on the properties of SnS:Cu, thin films, with potential application in the development of Solar Cell. Also some simulation data are reported.
Point 1. The concept of the study is of interest for the solid state readership. My major concern relies on the numerical study. I have the feeling that the simulation data are partially connected with the experimental one. Details on the numerical computations are missed and it is not quite obvious how these are related with the experiment.
For example, it is stated (line 350) that: It is worth mentioning that the parameters were optimized, how these properties were optimized and why ?
Response 1. Dear reviewer, the Solar Cell structure proposed is based on previously published work. Only we used it to evaluate our material as an absorbent layer inside the already described and evaluated device. We believe that to give credit to these works, we omit computational details but include references, and with this, we focus on results of the behaviour of our material. However, we include some descriptions in section 2.4 (lines 154 - 180).
The optimization thing refers to the fact of adjusting our experimental parameters with parameters of the same material (obtained by other techniques) given in the mentioned works and that was not considered in our investigation. All parameters together define the absorbent layer and must be coupled with the other layers of material inside in the solar cell structure proposed in order to SCAPS Software can reproduce them without giving us convergence failure trying to run those values.
Point 2. A few misprints were found, e.g line 365 Sns absorbent layer-> SnS
Response 2. Error Corrected: line 405. Sns --->SnS
Point 3. line 363 300-K -> 300K,
Response 3. Error Corrected: line 404. 300-K --->300K
Point 4. line 383 um ?
Response 4. Error Corrected: line 424. um ---> µm
Point 5. Lines 387-389, the following sentence is unclear: Figure 9 shows how efficiency then starts to increase with the increase in Cu-doped Sns 387thin layers thickness because this thicker layer will absorb more photons and generate 388more electron–hole pairs
Response 5. We rephrase that part of the text hoping that this idea can be expressed in a better way.
“As shown in figure 9 and table 7, the increase in the thickness of the SnS: Cu layer provokes efficiency rises of the simulated solar cell for all cases. This can be because an absorbing layer having a higher thickness allows more photons to be absorbed and increases the probability more electric carriers can be generated.
Line 439-442.
Point 6. Line 348 "The properties of the other layers are based on the parameters reported by Mimbashi et al., while in line 351, Minbashi et. al.
Response 6. Error Corrected: Mimbashi et. al. ---> Minbashi et al.
Author Response File: Author Response.pdf
Reviewer 3 Report
I have checked the manuscript in detail. In this interesting manuscript, the analysis is all right and the results seem correct. The manuscript is well-written and well-structured. It can be accepted for publication with minor changes without any further revision if the author addresses the followings suggestion.
- Add some real-life applications in the Abstract section.
- There is some latest reference seen in the introduction section. It is better to add the latest references and delete the old ones. Also, add some reference to the journal in which the author wants to publish a paper that shows their interest in the journal.
- Describe the model figure in detail.
- What will happen if you increase the value of λ?
- This paper is lacking novelty. So write down the novelty in a better way.
- It’s better to add some tabular comparison as well.
- There is much software why you choose SCAPS software.
- Add and explain how this work is important practically.
- There are some grammatical and typo errors that need to be removed.
- It’s better to add nomenclature.
Comments for author File: Comments.pdf
Author Response
Comments and Suggestions for Authors
I have checked the manuscript in detail. In this interesting manuscript, the analysis is all right and the results seem correct. The manuscript is well-written and well-structured. It can be accepted for publication with minor changes without any further revision if the author addresses the followings suggestion.
Point 1. Add some real-life applications in the Abstract section.
Response 1. line 26-27. Real-life applications have been added in the abstract section
Point 2. There is some latest reference seen in the introduction section. It is better to add the latest references and delete the old ones. Also, add some reference to the journal in which the author wants to publish a paper that shows their interest in the journal.
Response 2. Some of the less significant references with publication dates prior to 2010 have been removed to preserve a majority of more recent references.
[4] Devika, M., Reddy, N. K., Ramesh, K., Gunasekhar, K. R., Gopal, E. S. R., & Reddy, K. T. R. Low Resistive Micrometer-Thick SnS:Ag Films for Optoelectronic Applications. Journal of The Electrochemical Society 2006, 153(8), G727. doi:10.1149/1.2204870
[13] Tanusevski, A. Optical and photoconductive properties of SnS thin films prepared by electron beam evaporation. Solar Energy Materials and Solar Cells 2003, 80(3), 297–303. doi:10.1016/j.solmat.2003.06.002
References of coatings and nanomaterials magazines have been added to the introduction section both being part of the MPDI journals.
Line 41. Qu, Z., Wang, L., Tang, H., Ye, H., & Li, M. Effect of Nano-SnS and Nano-MoS2 on the Corrosion Protection Performance of the Polyvinylbutyral and Zinc-Rich Polyvinylbutyral Coatings. Nanomaterials 2019, 9(7), 956. doi:10.3390/nano9070956
Line 59. Gedi, S., Minnam Reddy, V.R., Alhammadi, S., Moon, D., Seo, Y., Kotte, T.R.R., Park, C., Kim, W.K. Effect of Thioacetamide Concentration on the Preparation of Single-Phase SnS and SnS2 Thin Films for Optoelectronic Applications. Coatings 2019, 9, 632. https://doi.org/10.3390/coatings9100632
Line 60. Di Mare, S., Menossi, D., Salavei, A., Artegiani, E., Piccinelli, F., Kumar, A., … Romeo, A. SnS Thin Film Solar Cells: Perspectives and Limitations. Coatings 2017, 7(2), 34. doi:10.3390/coatings7020034
Point 3. Describe the model figure in detail.
Response 3. Lines 163-174. The model figure has been described naming the layers of the solar cell and their function.
Point 4. What will happen if you increase the value of λ?
Response 4. Increasing the λ value may imply that the incident rays in the samples are not even of the order of X-rays. That said, it may be that the matter does not react in the same way and that the diffraction effect cannot be caused for the atomic structure of the material.
If the change in the lambda value in the diffractometer is just minimal, this can cause mismatches in the diffractograms, perhaps causing a gap in the position of the peaks and a change in value for their intensity.
Point 5. This paper is lacking novelty. So write down the novelty in a better way.
Response 5. Lines 79-85. A new paragraph has been prepared as well as certain modifications to the text so that the novelty of the work can be presented with more impact.
Point 6. It’s better to add some tabular comparison as well.
Response 6. Line 428. A table (Table 7) comparing the efficiencies of the solar cells with the change of the thickness in the absorber layer has been added so that the obtained values can be better appreciated.
Point 7. There is much software why you choose SCAPS software.
Response 7. Line 70-76. A paragraph was modified to highlight the advantages of the SCAPS software for our research purpose.
Point 8. Add and explain how this work is important practically.
Response 8. Line 469-472. The practical uses of the work results have been restructured and reviewed in the manuscript conclusions
Point 9. There are some grammatical and typo errors that need to be removed.
Response 9. Errors Corrected (Among others):
line 369. Sns --->SnS
line 404. 300-K --->300K
line 424. um ---> µm
line 448. Imagens ---> Images
line 399. (Table 5) cm2 and cm3 ---> cm2 and cm3
Point 10. It’s better to add nomenclature.
Response 10. line 495. Nomenclature has been added.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I still have the problem regarding the band gap determination from spectrophotometric data presented in Figure 6. I do not understand the answer you provided. It is obvious from Figure 6a, for the undoped sample (without Cu) that Eg is not correctly derived. They modified the sentence describing the shift of the absorption edge toward lower wavelengths for this sample that is OK but now it is obvious that Eg must be higher. However the Eg for this sample is the lowest.
Authors modified equation (4) to include R but they did not modify absorption coefficient claiming that R was already included in the coefficient calculations.
These facts make the feeling that the results on optical properties were not treated with sufficient attention and precision.
Author Response
I still have the problem regarding the band gap determination from spectrophotometric data presented in Figure 6. I do not understand the answer you provided. It is obvious from Figure 6a, for the undoped sample (without Cu) that Eg is not correctly derived. They modified the sentence describing the shift of the absorption edge toward lower wavelengths for this sample that is OK but now it is obvious that Eg must be higher. However the Eg for this sample is the lowest.
We are sorry to hear that the first explanation for this observation could not cover the question. We want to explain entire to you the criterium that we took to derive Eg in the sample 0% used in both manuscripts.
It is true that considering the entire range of the graph of α*hv vs hv, the value of Eg would increase, reaching the value of 3.51 eV. However, this value doesn't correspond to values reported in the literature for the same material. For this reason, we consider choosing a smaller region of the graph of α*hv vs hv, where the points can be adjusted to values of Eg with greater sense reported in the literature.
We include the original graphic corresponded to the sample y = 0% to explain what we did. We include the original graphic corresponded to the sample y = 0% to explain what we did. We use dashed lines to show the selected region to obtain the Eg value of the manuscript.
imagen in the attachment
We understand that you disagree with our criterium; for this reason, we add, in “Track Changes”, the corresponding modifications to the manuscript considering the new value of Eg for the undoped sample (y = 0%), to allow you to choose the version that convinces you.
The changes have been modified mainly the optical properties (section 3.4) and the Results of SCAPS simulation (section 3.6).
The changes are visualized in:
Line 22-24.
Line 329,331-343.
Line 378-379, 386.
Table 5.
Figure 8
Table 6
Figure 9
Table 7
Line 461-463.
Considering a very high value of Eg for an absorber layer shows a clear disadvantage in a photovoltaic device. That is, the J-V curves of y = 0% within the simulation section in SCAPS have been removed due to convergence problems within the program.
We add the table of values in order to you can corroborate that we have derived Eg correctly and only consider a less region than complete spectrum to this sample.
Table 1 in the attachment
Authors modified equation (4) to include R but they did not modify absorption coefficient claiming that R was already included in the coefficient calculations. These facts make the feeling that the results on optical properties were not treated with sufficient attention and precision.
Concerning optical properties. We made two mistakes, and we apologize. First, for not wanting to use the same graph as [22], we do not consider fig 6(c) in this writing. Second, we used an incorrect equation (4). Both errors were coupled and created confusion. However, the calculations of Eg always considered reflectance since the past paper ([22]).
Author Response File: Author Response.pdf
