Intermediate‐Site Anchoring Ligands Enable Robust Nonlayered Interfacial Passivation for Efficient and Stable Air‐Processed Perovskite Solar Cells

The complex moisture–oxygen environment in air places stringent demands on surface passivation for air‐processed perovskite solar cells. However, most conventional ammonium ligand‐based passivation, which binds to the perovskite surface through a terminal site, often induces ligand intercalation, elevates interfacial resistance, and compromises environmental stability, thereby limiting efficient device fabrication under ambient conditions. In this study, we report a robust, ligand‐based, intermediate‐site anchoring strategy for nonlayered interfacial passivation using a series of choline derivatives. The thioacyl sulfur coordinates strongly with under‐coordinated Pb 2+ sites, while iodide counter‐anions assist in halide vacancy healing, collectively forming a thermally robust and electronically homogeneous top interface. The surface passivation homogenizes surface potential, optimizes band alignment, relaxes residual strain, and suppresses trap‐assisted recombination and halide migration. Consequently, the resulting perovskite solar cells achieve a power conversion efficiency (PCE) of 26.54%, the highest value for air‐processed n–i–p PSCs reported so far. These devices also retained over 90% PCE after 2000 h at 65°C and 90% under continuous maximum power point tracking for 1000 h (AM 1.5G, 40°C ± 1°C), with projected T 80 lifetimes of ∼9800 h under illumination and ∼11 000 h under thermal aging, among the most stable air‐processed perovskite solar cells reported to date.