Numerical Design and Charge Transport Layer Optimization of Lead-Free Cs3Sb2I9 PSCs: Toward Experimental Efficiency Enhancement

Lead-free perovskite solar cells have become promising materials in the solar energy field; however, there are some constraints limiting their efficiency, like unfavorable band alignment, high defect densities, and inefficient charge extraction. Cs3Sb2I9 is a lead-free material that has excellent stability, but its experimentally reported efficiencies remain low (<4%). Therefore, Cs3Sb2I9 device performance was investigated using the one-dimensional Solar Cell Capacitance Simulator (SCAPS-1D), where the planar n–i–p structure was analyzed, focusing on its band alignment, transport layers, and key device parameters. The optimized device achieved a power conversion efficiency (PCE) of 13.62%, an open circuit voltage (Voc) of 1.37 V, a short circuit current density (Jsc) of 11.77 mA/cm2, and a fill factor (FF) of 84.15% with a 180 nm PCBM electron transport layer, a 150 nm Cu2O hole transport layer, and a 500 nm absorber thickness. This study advances the development of efficient lead-free perovskite solar cells, promoting sustainable and clean energy.