Performance Optimization of Lead‐Free (CH ₃ NH ₃ ) ₃ Bi ₂ I ₉ ‐Based Perovskite Solar Cell: A SCAPS‐1D Study

Perovskite solar cells (PSCs) have captured significant attention from the photovoltaic industry due to their superior efficiency and low‐cost manufacturing. The toxicity of lead‐based perovskites poses environmental concerns. In this context, the Pb‐free perovskite methylammonium bismuth iodide (CH 3 NH 3 ) 3 Bi 2 I 9 , presents a viable alternative to the Pb‐based halide cells, offering a harmless nature and exceptional durability. We have investigated the intrinsic impacts of (CH 3 NH 3 ) 3 Bi 2 I 9 perovskite by employing SCAPS‐1D. We optimized different parameters like thickness of the absorber layer, defect density ( N t ), energy bandgap, temperature, and carrier density of electron transport layer (ETL) and HTL, which affect device performance. We also investigated the effect of diverse HTLs and ETLs on the device's performance. The simulation results show an efficiency of 18.14% with V OC of 1.67 V, J SC of 12.72 mA cm −2 and FF of 85.16%, for the configuration FTO/WS 2 /(CH 3 NH 3 ) 3 Bi 2 I 9 /NiO/Pt, with a thickness of 500 nm and defect density ( N t ) of 10 14 cm −3 at a temperature of 300 K. These findings suggest that (CH 3 NH 3 ) 3 Bi 2 I 9 ‐based PSC is a promising device for future sustainable solar energy technology.