Permeable Modification and Near‐Infrared Absorption of n‐Type Non‐Fullerene Acceptors for High‐Performance Perovskite Solar Cells

As the foremost electron transport material in inverted perovskite solar cells, the phenyl‐C61‐butyric acid methyl ester (PCBM) is constrained by its inadequate electrical properties and defect passivation capability to fabricate devices with better performance. Herein, a non‐fullerene acceptor molecule eC9‐2Cl is introduced into the PCBM, which simultaneously passivates the defects distributed on the perovskite surface, enhances the electrical properties of PCBM, and provides additional near‐infrared absorption. The strategic incorporation of eC9‐2Cl optimizes band alignment and increases electron mobility. Furthermore, the electron‐deficient thiophene and carbonyl moieties in eC9‐2Cl effectively passivate uncoordinated Pb 2+ defects. The eC9‐2Cl‐doped PCBM devices showed an increased open‐circuit voltage ( V OC ) of 1.12 V, attaining the champion power conversion efficiency (PCE) of 24.40% with a narrow distribution. Moreover, the modified devices demonstrate an exceptional retention of 96% initial PCE after storing under ambient air for over 1800 h. This can be attributed to the enhanced uniformity, defect passivation, and augmented hydrophobicity after eC9‐2Cl introduction.