Crystallization Modulation Through Electron Transport Layer Surface Reconstruction Enables High‐Performance Full‐Air‐Processed Perovskite Solar Cells

Abstract The quality of the buried interface critically determines the performance of perovskite solar cells (PSCs). Herein, a homogenization strategy for the tin oxide (SnO ₂ ) electron transport layer (ETL) based on surface reconstruction is developed to enable mesoscale interface manipulation. By introducing the natural L‐carnosine (LC) at the buried interface, we achieve homogenized photon and electron transport through surface optimization of the SnO ₂ ETL. Additionally, the multi‐active sites in LC establish interlayer bridging and optimize interfacial contact, simultaneously passivating interfacial defects, mitigating residual stress, and improving carrier dynamics. Furthermore, LC modification regulates perovskite crystallization kinetics through multiple bonding mechanisms, facilitating the growth of high‐quality perovskite films. Ultimately, the champion device fabricated entirely in air achieves a power conversion efficiency of 25.30%, one of the highest efficiencies reported for air‐processed n‐i‐p structured PSCs. The optimized device without encapsulation exhibits enhanced stability under ISOS protocols, retaining 91.03% of its initial efficiency after 3192 h at 30 ± 5% relative humidity, 90.71% after 1512 h of thermal aging at 65 °C, and 90.17% after 1000 h of continuous maximum power point tracking under one‐sun illumination.