Chiral Molecular Engineering for Synergistic Defect Passivation and Phase Stabilization Enables 22.19%‐Efficient Inorganic Perovskite Solar Cells

ABSTRACT Chiral materials exhibit unique optoelectronic properties due to their non‐centrosymmetric structure. However, the influence of chiral configurations on halide vacancy repair and phase stability remains poorly understood, hindering the development of effective chiral passivation strategies for all‐inorganic perovskite solar cells. In this work, we rationally constructed chirality‐mediated interfaces between the perovskite and hole transport layer using R‐/S‐N‐(9‐fluorenylmethoxycarbonyl)‐allylglycine (RAC‐NFA) to simultaneously suppress defect‐mediated non‐radiative recombination and phase instability in CsPbI 3‐x Br x solar cells. Theoretical and experimental analyses reveal that RAC‐NFA operates via a “stereoselective complementarity” mechanism, which not only inhibits halide vacancy formation through “lock‐and‐key” coordination but also drives thermodynamically favorable secondary crystal growth and surface reconstruction, leading to larger, high‐quality grains. Additionally, the densely packed aromatic Fmoc groups at grain boundaries effectively suppress phase transition and moisture/oxygen penetration. RAC‐NFA modification further optimizes band alignment to enhance hole extraction and transport. Through these synergistic effects, the CsPbI 3‐x Br x device achieves a power conversion efficiency of 22.19%, among the highest reported for such materials, while retaining over 90% of its initial efficiency after 800 h in ambient air. This work presents a synergistic passivation strategy that concurrently improves efficiency and stability, offering a promising route toward the commercialization of perovskite photovoltaics.