The doping density of the HTM layer significantly affects the charge transport and recombination at the HTM/absorber interface. As shown in Figure , an increase in HTM doping density leads to improved short-circuit current density (Jsc), fill factor (FF), and PCE. Open-circuit voltage (Voc) also increases with higher doping densities up to an optimal level but declines beyond this due to increased Auger recombination and the formation of trap states at excessively high doping densities , . In the case of V2O5, an optimal doping density of 1×10 19 cm -3 was identified, resulting in a maximum PCE of 23.62%. This improvement is attributed to enhanced hole mobility and a stronger built-in electric field, which reduces recombination losses and facilitates efficient hole transport . Similar findings in the literature confirm that a high doping density in HTMs improves overall device performance, provided recombination losses are minimized . The absorber layer, CsSnI3, exhibits a different response to variations in doping density compared to the HTM. As shown in Figure , increasing the absorber doping density initially causes a decline in Jsc, FF, and PCE due to increased recombination losses and a reduction in carrier diffusion length. However, Voc shows an increasing trend because higher doping enhances the built-in potential at the absorber/ETM interface , , . Interestingly, when the absorber doping density exceeds 1×10 18 cm -3 , the FF begins to recover due to improved charge transport, despite recombination. The optimal doping density for the absorber was found to be 1×10 16 cm -3 , where a maximum PCE of 25.90% was achieved. This result aligns with studies showing that lower doping densities in absorber layers minimize recombination and maintain long carrier diffusion lengths .