Simulation‐Based Performance Analysis of Lead‐Free Bismuth Perovskite Solar Cells: A Comparative Study of Cs3Bi2I9 and (CH3NH3)3Bi2I9 ‐based Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs) have emerged as promising candidates in PV research due to their exceptional photovoltaic properties. However, the toxicity and environmental concerns associated with lead‐based perovskites have led to the exploration of lead‐free alternatives. In this study, the performance of lead‐free bismuth PSCs, specifically PSCs based on Cesium Bismuth Iodide (Cs 3 Bi 2 I 9 ) and Methyl Ammonium Bismuth Iodide (MA 3 Bi 2 I 9 ), is investigated. Numerical simulations using the solar cell capacitance simulator (SCAPS) are conducted to comprehensively analyze the influence of key parameters, including the band‐to‐band radiative recombination rate, the absorber layer defect density, the absorber layer/electron transport layer (ETL) interface defect density, the absorber layer/hole transport layer interface (HTL) defect density, operating temperatures, and series and shunt resistances, and to optimize the proposed PSCs accordingly. The simulation results demonstrate a significant impact of these key parameters on the performance of Cs 3 Bi 2 I 9 and MA 3 Bi 2 I 9 PSCs. The optimized Cs 3 Bi 2 I 9 ‐based PSC exhibited notable performance characteristics, including a PCE of 13.81%, a V oc of 1.16 V, a J sc of 18.14 mA cm −2 , and FF of 65.51%. In contrast, the MA 3 Bi 2 I 9 ‐based PSC demonstrated relatively lower performance, with a PCE of 11.82%, V oc of 1.14 V, J sc of 18.06 mA cm −2 , and FF of 57.33%. The study on the defect density at the interfaces revealed the performance of PSCs is predominantly influenced by defects at the front interface (ETL/Absorber) rather than the rear interface (HTL/Absorber). These results provide valuable insights for the experimental design and optimization of lead‐free bismuth PSCs.