Engineering the Absorber Architecture for High‐Efficiency Lead‐Free Inorganic Perovskite Solar Cells in a Trilayer Two‐Terminal Design

In this study, a high‐efficiency trilayer perovskite solar cell is proposed, analyzed, and optimized. Initially, the absorber layer is selected by comparing the external quantum efficiency of monolayer, bilayer, and trilayer configurations, with the trilayer structure demonstrating superior performance. Subsequently, thickness optimization of each absorber layer is conducted, leading to an optimized design featuring Cs 3 Bi 2 I 9 (top, 0.4 μm), CsSnBr 3 (middle, 0.8 μm), and CsSnI 2 Br (bottom, 0.5 μm). SnO 2 and Cu 2 BaSnS 4 are employed as the electron transport layer and hole transport layer, respectively. The optimized device exhibits an outstanding open‐circuit voltage ( V oc ) of 1.46 V, a short‐circuit current density ( J sc ) of 30.40 mA cm −2 , and a fill factor of 82%, resulting in a remarkable power conversion efficiency of 36.3%. These findings highlight the promise of carefully engineered trilayer, lead‐free perovskite architectures for next‐generation, high‐efficiency, and environmentally sustainable solar cells.