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 Pb²⁺ 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.