<p>This study focuses on optimizing the efficiency of lead-free perovskite solar cells (PSCs) using CH₃NH₃SnI₃ as the active layer. Various modifications were investigated to enhance the performance of the PSCs. Key adjustments included the choice of polymer as a hole-transporting material (HTM), electrode materials, device structure, and the incorporation of a thin layer of nickel oxide (NiO) as a hole-selective layer (HSL). The results demonstrate that replacing ZnTe with TAPC polymer as the HTM led to a significant increase in power conversion efficiency (PCE) due to better band alignment and electron-blocking properties. Additionally, substituting the expensive gold electrode with aluminum was facilitated by incorporating a PEDOT conductive polymer buffer layer to improve carrier extraction efficiency. Transitioning from a traditional n-i-p structure to a p-i-n inverted structure and optimizing TiO₂ placement further enhanced light absorption and device current. The introduction of a thin NiO layer, optimized at 5&#xa0;nm thickness, contributed to improved PCE, short-circuit current density (J_sc), and open-circuit voltage (V_oc). Ultimately, the optimized PSC structure yielded an impressive PCE of 12.37%, indicating a substantial advancement in efficiency compared to previous studies. These findings underscore the potential of lead-free perovskite materials, particularly CH₃NH₃SnI₃, in revolutionizing solar energy technology toward a more sustainable and efficient future.</p>