Enhancing Indoor Photovoltaic Efficiency to 37.6% Through Triple Passivation Reassembly and <i>n</i>‐Type to <i>p</i>‐Type Modulation in Wide Bandgap Perovskites

Abstract Despite well‐matching indoor illumination spectra, the performance of wide bandgap perovskite solar cells (WB‐PSCs) for indoor photovoltaics (i‐PV) is hindered by photo‐induced halide phase segregation and trap‐assisted non‐radiative recombination. Herein, a Triple Passivation Treatment (TPT) reassembly strategy is presented to simultaneously suppress bulk and surface defects. TPT induces a transition in perovskite surface energetics from n ‐type to p ‐type and remarkably increases the photoluminescence quantum yield from 0.5 to 2.1%, creating a more favorable band alignment for hole extraction whilst substantially reducing halide phase segregation. As a result, 1.75 eV WB‐PSCs achieve an indoor Power Conversion Efficiency (iPCE) of 37.6% under 1000 lux illumination. Under standard sunlight conditions, the devices reach a Power Conversion Efficiency (PCE) of 20.1% and a fill factor of 78.5%, among the best performance parameters for this bandgap. Importantly, the passivated devices exhibit excellent shelf stability, retaining 92% of their initial performance after 3200 h. Under ambient air conditions at 55 °C, the unencapsulated devices maintained 76% of their initial PCE after 300 h continuous light soaking. The findings represent a significant breakthrough in the development of stable WB‐PSCs for i‐PV applications, with minimized nonradiative losses and enhanced performance.