Interface Passivation and Morphology Regulation of Fullerene‐Based Perovskite Solar Cells for Enhancing Device Performance by phenethylammonium iodide

While [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM)/bathocuproine (BCP) is widely used as an electron transport stack in inverted perovskite solar cells (PSCs), its interfacial properties remain insufficiently studied. To clarify whether this interface can be optimized to enhance device performance, this work implements a targeted interfacial passivation strategy utilizing a phenethylammonium iodide (PEAI) interlayer to optimize the PCBM/BCP contact and energy alignment. Density functional theory (DFT) calculations reveal that the adsorption configuration of PEAI on PCBM is dominated by hydrogen bonding between the ammonium group of PEAI and the carbonyl group of PCBM, with an adsorption energy of −1.501 eV. This interfacial modification effectively regulates the PCBM surface morphology, homogenizes interfacial potential distribution, and improves energy level alignment. Mechanistic investigations further indicate that PEAI suppresses trap‐assisted recombination while promoting interfacial charge extraction. This optimized strategy yields a power conversion efficiency (PCE) of 22.92% for PSCs based on a 1.62 eV triple‐cation mixed‐halide perovskite absorber, with open‐circuit voltage and fill factor reaching 1.18 V and 84.78%, respectively. Furthermore, PEAI‐passivated devices retain 94.1% of their initial PCE after 150 h of continuous illumination. This work establishes a feasible and efficient interface engineering strategy for high‐performance and short‐to‐medium‐term stable inverted PSCs.