Iodide Management and Oriented Crystallization Modulation for High‐Performance All‐Air Processed Perovskite Solar Cells

Halide-related defects at the buried interface not only cause nonradiative recombination, but also seriously impair the long-term stability of perovskite solar cells (PSCs). Herein, a bottom-up, all-in-one modification strategy is proposed by introducing a multisite antioxidant ergothioneine (EGT) at the buried interface to manage iodide ions and manipulate crystallization dynamics. The findings demonstrate that EGT not only passivates uncoordinated Sn⁴⁺/Pb²⁺ defects, but also firmly anchors iodide ions and inhibits their oxidation to I₂. Additionally, the modification by EGT enhances the oriented crystallization of perovskite, improves the carrier dynamics, and releases residual stresses. Consequently, the optimized all-air processed device (Rb_0.02(FA_0.95Cs_0.05)_0.98PbI_2.91Br_0.03Cl_0.06) achieves a remarkable power conversion efficiency (PCE) of 25.13%, which is among the highest values reported for devices fabricated in air, along with ultrahigh open-circuit voltage (V_OC) of 1.191 V and fill factor (FF) of 84.9%. The optimized device without encapsulation exhibits strong humidity, thermal, and operational stability under ISOS protocol. Specifically, the initial efficiency of the device is retained at 90.12% after 1512 h of thermal ageing at 65 °C and 90.14% after 930 h of continuous maximum power point tracking (MPPT) under simulated AM1.5 illumination.