Review Reports

Round 1

Reviewer 1 Report

The authors report a numerical study on how the performance of some materials can be exploited as solar  cells.

The concept is interesting but lacks of understanding, reproducibility and consistency. For example, any pitfalls of the numerical model applied are missed, lack of the accuracy and range of application is missed as well as.

The most important and crucial part is the validation of the model. How sensitive is the model to changes of input data of tables 1 & 2?

Please, take care of the formatting in several parts of the draft (e.g p. 2, 4(table 1),8 (line 246) )

 

 

Author Response

The authors report a numerical study on how the performance of some materials can be exploited as solar cells.

Comment 1: The concept is interesting but lacks of understanding, reproducibility and consistency. For example, any pitfalls of the numerical model applied are missed, lack of the accuracy and range of application is missed as well as.

Response: Thank you very much. In the introduction part of the revised manuscript, we have provided the above information. The simulator SCAPS-1D is used to make many solar cell simulations which can be utilized to match the experimental work. Thus, it can be used to reliably simulate the solar cells provided that they are one dimensional and it uses the thickness of layers only, not the depth and width of layers is its biggest pitfall. It also depends on the structure we are using and the defined parameters. We have to select the input parameters carefully and can get the same results obtained experimentally. The software generally uses the fundamental Semiconductor theory, principle and formulas explained in the introduction part.

Comment 2: The most important and crucial part is the validation of the model. How sensitive is the model to changes in input data of tables 1 & 2?

Response: SCAPS is very sensitive to the input parameters. The software solves the equation numerically with appropriate boundaries and initial conditions. Therefore, the input material parameters may possess extreme values causing non-convergence. In most cases, proper thickness values, Nc, Nv, N_D, N_A, or Eg value eliminate the problem.

Comment 3: Please, take care of the formatting in several parts of the draft (e.g p. 2, 4(table 1),8 (line 246) )

Response: The formatting has been corrected in the revised manuscript, as said above by the reviewer.

 

 

Reviewer 2 Report

This study is tested Sb2Se3 photovoltaic model with different HTLs studied by simulation software-SCAPS. It is important to develop Sb2Se3 type absorber layers and test diffent HTLs. However, this theoretical paper is hard to follow for the audience with many input and output parameters and it should be improved. Morever, it is highly expected final conclusion that Spiro-OMeTAD is the best HTM as observed previously.

Abstract should be improved. “In this work, we compare the behaviour of typical organic (P3HT: PCBM and Spiro-OMeTAD) and inorganic (CuSCN) hole transport materials (HTMs) and analyze their influence on device performance.” This does not explain or summarize the manuscript. Antimony selenide is absorber layer and it should be mentioned at the beginning of the text.

Equations given in page two were not legible since they are justified in manuscript.

It is not possible to understand how simulation software reach main outputs: Voc, efficiency and FF by using first three equations.

It should be clear what is the source of each input parameters of the different layers of solar device given in Table 1.

It is useful that authors included effect of many different factors. However, it is not clear that how software calculated the effect of each parameter. As an example, effect of back contact is given at page 6, still we cannot see how simulation software included this effect in the equations. Since this is a simulation study, it is important to give where we get input parameters and how we reached outputs for each parameter and reflect it to the efficiency data.

Moderate editing of English language required.

Author Response

This study is tested Sb₂Se₃ photovoltaic model with different HTLs studied by simulation software SCAPS. It is important to develop Sb₂Se₃ type absorber layers and test different HTLs. However, this theoretical paper is hard to follow for the audience with many input and output parameters and it should be improved. Moreover, it is highly expected final conclusion that Spiro-OMeTAD is the best HTM as observed previously.

Response: The paper has been revised and corrected as said by the reviewers. The abstract and introduction part has also been improved. In the present work, P3HT: PCBM-based HTM has been removed, and CuI as an inorganic hole transport material is added. The CuI-based structure shows a maximum efficiency of 23.48 %.

Comment 2: Abstract should be improved. “In this work, we compare the behaviour of typical organic (P3HT: PCBM and Spiro-OMeTAD) and inorganic (CuSCN) hole transport materials (HTMs) and analyze their influence on device performance.” This does not explain or summarize the manuscript. Antimony selenide is absorber layer and it should be mentioned at the beginning of the text.

Response: The abstract has been revised and corrected as said above by the reviewer.

Comment 3: Equations given in page two were not legible since they are justified in manuscript.

Response: Thank you so much. More information related to these equations has been added in the introduction.

Comment 4: It is not possible to understand how simulation software reaches main outputs: Voc, efficiency and FF by using first three equations.

Response: The manuscript has been revised and corrected. The information about the simulation part is added step by step in the introduction.

SCAPS solves the basic semiconductor equations in 1-Dimension under steady-state conditions. The simulator is worked on the simultaneous resolution of equations for electrons and holes, as shown in equations (1-5)

 + [ p(x)- n(x) + N_D - N_A +                    (1)

 = (G - R)                                                                  (2) 

   =  (G - R)                                                                  (3)

Here Ψ is electrostatic potential, ε is the permittivity, q is the electron charge, n(x), p(x), and ρ shows the concentration of electrons, holes, and density of charge carriers, respectively. N_D and N_A are donor and acceptor impurities, R and G are recombination and generation rates, Jn and Jp are the current densities of electrons and holes.

                                                                 (4)

                                                                     (5)

Together with appropriate boundary conditions at the interfaces and contacts, this results in a system of coupled differential equations in (Ψ, n, p) or (Ψ, EFn, EFp).

SCAPS numerically calculates this system's steady state and a small signal solution. Hereto, the structure is first discretized (creating a mesh). A steady state working point situation is calculated, and a small signal analysis is performed when required.

 

 

Comment 5: It should be clear what is the source of each input parameters of the different layers of solar device given in Table 1.

Response: All the parameters for each layer are taken from the literature mentioned in the revised manuscript.

Comment 6: It is useful that authors included effect of many different factors. However, it is not clear that how software calculated the effect of each parameter. As an example, effect of back contact is given at page 6, still we cannot see how simulation software included this effect in the equations. Since this is a simulation study, it is important to give where we get input parameters and how we reached outputs for each parameter and reflect it to the efficiency data.

Response: Thank you very much. First, the working point specifies the parameters not varied in a measurement simulation and are relevant to that measurement. The series and shunt resistance values can be introduced on the action panel. Then for each layer, the properties are introduced, and back -the front contact’s properties are also adjusted, as shown below. The table for front and back contact properties is also added in the revised manuscript, as said above by the reviewer. Then, the voltage V: is discarded in I-V and C-V simulation. It is the dc-bias voltage in C-f and QE(() simulations. SCAPS always starts at 0 V and proceeds at the working point voltage in several steps that we also should specify.

In the action part of the Action Panel, we can select one or more of the following measurements to simulate: I-V, C-V, and QE(l). Then, the Energy Bands Panel opens, and the calculations start and obtain the I-V, C-V and QE plots.

 

Reviewer 3 Report

Dear Editor

The authors in this work have taken a numerical approach on Organic and Inorganic HTLs Based Solar Structures to investigate the performance of solar cells. 

In my opinion, there are several issues in this work that have to be fixed and corrected before it is being considered for publication.

Below are my major comments on the paper contents:

-       -   There are font and equation style inconsistencies in the manuscript. Please look at line 44-46 and 63-70.

-        -  This statement is incorrect “Poly(3-hexylthiophene): phenyl-C61-butyric acid methyl ester (P3HT: PCBM) [9] are the popular organic HTMs for up-and-coming solar devices”. PCBM is electron transporter not HTM. Please revise this throughout your paper.

- Authors can check the following papers to get more information:

https://doi.org/10.1016/j.tsf.2011.01.165

https://doi.org/10.14500/aro.11103

-          - Authors stated “P-type inorganic HTM, such as Copper-thiocyanate (CuSCN)” CuSCN is not inorganic but it is a coordination polymer/organic.

-          - This statement is not clear and incorrect “An I-V curve provides these solar cell parameters. Thus, we can say that the output current is at maximum power”

-          - The gaps/issues in the current researches on HTMs is not clear. Also, is not clear why authors have used this simulation approach.

-          - What are the main contributions of this work? These have to be given in the introduction

-          - Figure 1 must be fully revised. Authors claimed the use of P3HT:PCBM while it is not seen in the pictorial and energy levels of Figure 1.

-           - What is “e-parameters?

-          - Please correct “~105 cm1” to “~105 cm^-1

-          - On line 124 Change table 2 to Table 2

-          - Remove word varying in the tables.

-          -- Methodology is weak and not complete. Please explain how the simulation method was carried out in a step-by-step form.

-          - On line 129 HTL is misleading, please make sure you are using HTM through the manuscript. HTL is hole transporting layers that are not responsible for light absorption, but it is specifically used to block electrons.

-           - Figure 2(a) and (b) are not realistic. It is not possible to have similar Jsc and Voc for different absorbers. Please compare your results with experimental ones.

-          - On Line 271 please change Vbi to V_b

-          - It is not clear how the authors considered Rs and Rsh in the simulation? Please give explanation and plots of calculation.

-          - What is the nature of the devices investigated? Organic, inorganic, or hybrid?

-          - Title should be modified. There is no investigation on illumination spectrum in this work.

Minor editing of English language required.

Author Response

The authors in this work have taken a numerical approach to Organic and Inorganic HTLs Based Solar Structures to investigate the performance of solar cells. In my opinion, there are several issues in this work that have to be fixed and corrected before it is considered for publication. Below are my major comments on the paper’s contents:

      Comment 1: There are font and equation style inconsistencies in the manuscript. Please look at lines 44-46 and 63-70

      Response: The font and equations formatting has been corrected in the revised manuscript.

       Comment 2: This statement is incorrect “Poly(3-hexylthiophene): phenyl-C61-butyric acid methyl ester (P3HT: PCBM) [9] are the popular organic HTMs for up-and-coming solar devices”. PCBM is an electron transporter, not HTM. Please revise this throughout your paper. Authors can check the following papers to get more information: https://doi.org/10.1016/j.tsf.2011.01.165 ,https://doi.org/10.14500/aro.11103

       Response: Thank you very much for the valuable comments. The work has been revised and corrected. P3HT:PCBM has been removed from the present paper, and CuI has been added as this material helped to achieve the highest efficiency of 23.48 %.

       Comment 3: Authors stated “P-type inorganic HTM, such as Copper-thiocyanate (CuSCN)” CuSCN is not inorganic but it is a coordination polymer/organic.

       Response: In the revised manuscript, we have removed the terms “inorganic and organic” and used the term “various HTLs”.

    Comment 4: This statement is not clear and incorrect “An I-V curve provides these solar cell parameters. Thus, we can say that the output current is at maximum power”

       Response: The above sentence has been removed from the revised manuscript.

       Comment 5:  The gaps/issues in the current research on HTMs are not clear. Also, is not clear why the authors have used this simulation approach.

       Response: Sb₂Se₃ has the potential to develop into a competitive PV technology due to its appropriate optical bandgap, high optical absorption coefficient, stable binary phase, earth-abundant constitution, and low toxicity, even though its champion efficiency currently trails that of other well-developed solar cells. Many researchers have suggested that an HTL may be advantageous to reduce the carrier recombination loss at the rear surface in order to improve PV performance [Amin et al., 2007, Matin et al., 2013, Yang et al., 2016, Kazmi et al., 2020]. When constructing solar cells, intrinsic HTL characteristics like strong carrier mobility and good p-type conductivity are essential, but Sb2Se3/HTL energy level matching and HTL/back contact are also important. However, inefficient carrier transport and collection, besides interface recombination with many HTLs, still lead to a deficit of open-circuit voltage and short-circuit current, contributing to low PV efficiency. Thus, in the present work, we compared the three different HTMs (Spiro-OMeTAD, CuSCN and CuI)-based structures and concluded that if we use CuI as an HTM with a Sb₂Se₃ absorber, it will help in achieving the maximum efficiency as compared to widely used Spiro-OMeTAD and CuSCN. We have added this part to the revised manuscript, also.

 

      A strategy for comprehending physical functioning, evaluating the reliability of designed physical explanations, and assessing the effects of changes in physical parameters on the performance of solar cell devices is simulation. It is irrational to design a solar cell without modeling. It is time- and money-wasting because a simulator improves solar cell performance by lowering risks, spending less time and money, and assessing layer features and functions. That is why we used the simulation approach.

       Comment 6: What are the main contributions of this work? These have to be given in the introduction

       Response: In the introduction and conclusion part, the contribution of the present work has been added, as said above by the reviewer.

       Comment 7: Figure 1 must be fully revised. Authors claimed the use of P3HT: PCBM while it is not seen in the pictorial and energy levels of Figure 1.

       Response: Figure (1) has been revised, and all three HTMs (CuI, Spiro-OMeTAD and CuSCN ) energy levels have been added as the reviewer said.

       Comment 8: What are “e-parameters?

       Response: The” e-parameter” word is replaced by the "material parameters of each layer” in the revised manuscript.

       Comment 9: Please correct “~10⁵ cm¹” to “~10⁵ cm^-1

       Response: This has been corrected in the revised manuscript.

           Comment 10: On line 124 Change table 2 to Table 2

           Response:  This has been corrected in the revised manuscript.

          Comment 11: Remove word varying in the tables.

          Response: The varying word has been removed in the revised manuscript.

          Comment 12: The methodology is weak and not complete. Please explain how the simulation method was carried out in a step-by-step form.

          Response: In the introduction part, the simulation study has been revised and defined with the help of equations and other parts.

          Comment 13: On line 129 HTL is misleading, please make sure you are using HTM throughout the manuscript. HTL is a hole transporting layers that are not responsible for light absorption, but it is specifically used to block electrons.

         Response: Thank you so much. The “HTL” term has been revised with HTMs at the needful places of paper.

          Comment 14: Figures 2(a) and (b) are not realistic. It is not possible to have similar Jsc and Voc for different absorbers. Please compare your results with the experimental ones.

          Response: The work has been revised and corrected, and the results are varied now, as shown in the figures of the revised manuscript.

 Comment 15:  On Line 271 please change Vbi to V_b

         Response: In the revised manuscript, V_bi is changed by V_b, as said above by the reviewer.

       Comment 16: It is not clear how the authors considered Rs and Rsh in the simulation. Please give an explanation and plots of calculation.

        Response: From the action panel of the software, we can adjust the series and shunt resistance values, as shown below.

                 

        In the present paper, the range for series and shunt resistance are varied from 1-5 ohm-cm² and 300-1500 ohm-cm², respectively.

        Comment 17: What is the nature of the devices investigated? Organic, inorganic, or hybrid?

         Response: Present work is based on the simulation study of various HTLs/Sb₂Se₃-based solar structures. The ZnO/Sb₂Se₃/(CuSCN &CuI) heterostructure was analyzed as a candidate to act as an inorganic eta-solar cell, and Sb₂Se₃/Spiro-OMeTAD is hybrid.

        Comment 18: The title should be modified. There is no investigation of the illumination spectrum in this work.

        Response: In Fig 6(c), the effect of different illumination spectra on the device's efficiency is shown. More significance of these spectrums has been added in the revised manuscript. The title has been revised as said above by the reviewer.

 

Round 2

Reviewer 1 Report

The authors provided a solid report on several issues raised.

However, one issue needs further clarification

The authors replied that:

"SCAPS is very sensitive to the input parameters"

This means that the results could be "vulnerable" and each case needs special attention. How one can cope such issues ?

Author Response

Comment: SCAPS is very sensitive to the input parameters" This means that the results could be "vulnerable" and each case needs special attention. How one can cope with such issues?

Response: Thank you so much. SCAPS is very sensitive to the input parameters as the software solves the equation numerically with appropriate boundary and initial conditions. The most likely causes of convergence failure are contact characteristics, layer electron affinities, defect concentrations, defect energy distributions, and mobility values that are outside of the expected range. Aside from these, the performance of the device can typically be affected by a little change in Nc, Nv, N_D, N_A, or Eg values. Each layer's input parameters need to be double-checked, and the values must be changed to ones that are realistically attainable.

Reviewer 3 Report

Dear Edtior

The authors have performed almost all the required revisions. 

It is now accepted for publication.

Moderate editing of English language required

Author Response

The authors have performed almost all the required revisions. 

It is now accepted for publication.

Response; Thank you very much for your encouragement. Comments on the Quality of English Language

Moderate editing of English language required

Response: It has been done and highlighted in the revised manuscript.