Abstract <p>Perovskite solar cells (PSCs) demonstrate considerable promise for high-efficiency photovoltaic (PV) applications, owing to their exceptional light absorption characteristics and simple fabrication methods. The incorporation of lead-free CsSnCl₃, FASnI₃, and MASnI₃ enhances light absorption and charge-carrier generation, alongside suitable electron transport layers (ETLs) and hole transport layers (HTLs). This study is conducted in two phases: the initial phase focuses on identifying suitable ETL and HTL, using CsSnCl₃, FASnI₃, and MASnI₃ as the tripartite perovskite layer. In this process, a worst-case analysis has been conducted by incorporating defects into the material. The defects were introduced within the range 10¹² to 10¹⁸ to analyze the worst-case scenario and identify the appropriate ETL and HTL. The analysis revealed that the structure utilizing PEDOT : PSS as the HTL is more appropriate, achieving an efficiency range of 1.7 to 2.2% at the highest defect concentration. Secondly, the refined structure resulting from the worst-case analysis is optimized for improved efficiency. This results in the ideal configuration of FTO/PCBM/CsSnCl₃/FASnI₃/MASnI₃/PEDOT : PSS, obtaining an efficiency (η), <i>V</i>_oc,&#xa0; <i>j</i>_sc, and fill factor of 29.19%, 0.78 V, 50.99 mA/cm², and 73.62%, respectively, for the arrangement of 500/200/100/700/700/800 nm, with a defect concentration of 10¹⁵.</p>