Initially, the thickness of the hole transport material (HTM) layer, V2O5, was varied from 0.01 µm to 0.1 µm. Simulation results indicate that increasing the thickness of the HTM slightly improves the short-circuit current density (Jsc), likely due to enhanced charge transport. However, beyond an optimal thickness of 0.035 µm, other key parameters, such as open-circuit voltage (Voc) and fill factor (FF), start to decline. The increased thickness likely introduces additional series resistance and recombination losses, leading to a slight drop in overall efficiency. Based on these findings, the thickness of the V2O5 HTM was optimized to 0.035 µm to balance charge transport and minimize losses , . The absorber layer, CsSnI3, initially had a thickness of 0.5 µm. The thickness was then optimized to determine its effect on performance. As shown in Figure , the relationship between the absorber thickness and cell performance is non-linear. While a thicker absorber initially improves photon absorption and Jsc, further increases lead to recombination losses due to insufficient carrier diffusion length. Additionally, Voc and FF exhibit an inverse relationship with increasing absorber thickness, resulting in diminishing returns for PCE. The optimal thickness for the absorber layer was determined to be 0.275 µm, where the cell achieved a maximum PCE of 23.43%. This result aligns with previous studies indicating that the thickness of the absorber layer must balance light absorption and carrier extraction , . For the electron transport material (ETM), WS2, thickness optimization revealed a similar trend.