Bifunctional Molecular Bridge with Tunable Dielectric Constant for Air‐Processed Perovskite Solar Cells

ABSTRACT Most current research focuses solely on chemically passivating defects in air‐processed perovskite solar cells (PSCs), whereas the simultaneous use of effective chemical passivation and dielectric screening to further improve performance has not been explored. This study designs and introduces two bridging molecules with tunable dielectric constants—Ethanolamine sulfate (EAS) and Ethanolamine phosphate (EAP)—to synergistically modify the SnO ₂ /perovskite interface of n‐i‐p‐structured PSCs under ambient conditions. EAS and EAP feature dual active sites that establish an interlayer bridge, simultaneously passivating defects (e.g., uncoordinated Sn ⁴⁺ /Pb ²⁺ and oxygen vacancies), regulating crystallization kinetics, alleviating residual stress, and improving carrier dynamics. Owing to its stronger interaction with the SnO ₂ /perovskite layers and a higher dielectric constant, a champion power conversion efficiency (PCE) of 25.22% based on EAP modification is achieved—one of the highest reported values for air‐processed n‐i‐p PSCs—along with exceptional stability (e.g., 95.0% PCE retention after 4392 h storage, and 95% after 1000 h of MPPT at 40 ± 5°C and 40%–50% RH in air). This study provides valuable insights for the rational molecular design of interface engineering, enabling the fabrication of high‐performance, long‐lifetime PSCs in ambient air.