Impact of Indium\nDoping in Lead-Free (CH<sub>3</sub>NH<sub>3</sub>)<sub>3</sub>Bi<sub>2–<i>x</i></sub>In<sub><i>x</i></sub>I<sub>9</sub> Perovskite Photo

Hybrid halide perovskites (HHPs) have revolutionized\nthe field\nof solar cells due to their low cost, solution-processable synthesis,\nand exceptional device performance. Although lead (Pb)-based perovskites\nare currently the most efficient, their application in indoor photovoltaics\nand wearable electronics is limited by lead’s toxicity. This\nhas intensified the search for Pb-free alternatives, particularly\nfor use in portable electronic devices. In this study, we utilized\na vapor-assisted solution process to systematically engineer the composition\n of bismuth-based perovskite-inspired materials (PIMs) through indium\ndoping, forming homogeneous and pinhole-free (CH<sub>3</sub>NH<sub>3</sub>)<sub>3</sub>Bi<sub>2–<i>x</i></sub>In<sub><i>x</i></sub>I<sub>9</sub> (Bi–In) films. These\nbimetallic Bi–In perovskites exhibit enhanced properties, including\nhigh recombination resistance, reduced low-frequency capacitance,\nlower defect density, and minimal microstrain. Electrochemical impedance\nspectroscopy (EIS) shows significantly reduced ion migration in Bi–In\ncompositions compared with pure bismuth-based counterparts. The optimized\nBi–In-based solar cells achieved a power conversion efficiency\n(PCE) of 2.5% under outdoor illumination and 5.9% under indoor lighting,\nshowcasing their potential as promising lead-free alternatives for\nphotovoltaic applications.