The efficiency limit of perovskite cells
Paper Response
After studying the operation and physics behind photovoltaic solar cells, I have been able to use this knowledge to design and optimize different solar cells designs with Mathematica. It has also been exciting to compare different materials, for instance, thermally-grown silicon dioxide layer on silicon wafer (SiO2/Si) when compared to an indium Tin oxide (ITO) thin-film on glass. These models are all based on the three-layer thin-film interference model, on which the reflectance and transmittance of each material can be used to observe each material’s transparency.
As an exercise in the class Photovoltaic Engineering, I studied a paper on the efficiency limit of perovskite cells, in order to prove or disprove some of the authors main claims and findings.
The reviewed article and Mathematica Code with the paper response are below.
As highlighted in the Mathematica notebook’s section V and VI, the paper sheds light on important findings regarding perovskite cells and its efficiency when varying the thickness and the nature of the planar or textured cell. Table 1 and Figure 2 offer visual results that are valuable for scientists and people in the field, which could create important impact int the research field. Moreover, the explanations of the science behind the functioning of solar cells is good overall, as it clearly labels used formulas. Due to the amount of confirmed values, the paper should be accepted. Nevertheless, there are some minor and major changes which should be mandatory edits when sharing this paper onwards.
Firstly, there's a clear lack of transparency with the concept of θm and it's meaning. Figure 1 doesn’t provide enough information to understand this concept. Diagrams a) , b) and c) are also poorly labeled, where the reader doesn’t understand if they are defining rays inside or outside of the material. Moreover, the concept of the angular filter is very vague, it is hard to comprehend it’s dependency factor on λ, as well as a lack of formulas to prove the results on Figure 3.
Moreover, there are minor issues that while don't impede the confirmation of values like θm mentioned above does, create many difficulties to properly asses the article. Firstly, there are no mention of units along the paper, which can drastically change results. Moreover, there is an ambiguity as to what temperatures - the sun or the cell - are used in which thermal formulas. There is also a lack of basic necessary equations for the wavefactor, k , the fill factor, FF, and the efficiency, PCE. Moreover, an explanation of how the values of Jsc, Jmp and Vmp were extracted would be good for clarity, even if just in an Appendix. Even though it will mostly be scientist reading this article, it shouldn't be assumed that all readers have seen these concepts, as it is the goal to expand knowledge on the functioning of perovskite cells and reach all the possible readers to increase the interest on solar cell research. Finally, it is also important to mention that the boundaries stated in the article (from 0 to \[Infinity]) when integrating, are very likely not the ones that were used. There is no mention about the absorptance cutoff that semiconductors experience when photons have a wavelength above their bandgap. Moreover, there is only certain available data for the refractive index of perovskite material, specifically from 310nm onwards. For this reason, it should be explicitly stated in the article that even though the theoretical boundaries are from 0 to \[Infinity], the true boundaries used for this study are from 310nm to the wavelength at the energy bandgap. If on the other hand, techniques of extrapolation were used, then a mention of this would also be valuable.
Overall the paper is very successful at showing friendly figures and results, but when analyzing thoroughly all the process and trying to reproduce them, one realizes that many more details could be shared with the reader in order to make the paper more trustworthy and valuable.