Ion‐Defect Dual Management for Achieving Efficient Air‐Processed Perovskite Solar Cells With Certified Efficiency 27.1%

ABSTRACT Achieving high‐efficiency and durable perovskite solar cells (PSCs) under ambient fabrication remains a fundamental challenge due to the coupled instabilities arising from halide redox chemistry and Pb‐related defects. Here, we introduce a molecular “ion–defect dual‐management” strategy using N‐Acetylsulfanilyl Chloride (ABSC) that simultaneously regulates iodide redox species in precursor solutions and passivates electronic imperfections in the crystallized films. ABSC selectively induces the in situ formation of I 3 − without FA + deprotonation, while its multidentate functional groups strongly coordinate with undercoordinated Pb 2+ to suppress deep traps and enhance crystallinity. This synergistic regulation yields air‐processed inverted PSCs with a certified steady‐state efficiency of 27.10% and long‐term operational stability retaining over 98% of the initial performance after 1000 h of maximum power point tracking. Importantly, ABSC is fully compatible with vacuum flash‐evaporation, enabling scalable fabrication of large‐area flexible and bifacial modules exceeding 16% efficiency. Our findings establish a mechanistically grounded and industrially relevant route for stabilizing soft ionic lattices, advancing perovskite photovoltaics toward practical, high‐performance deployment.