Unavoidable charge defects at the interface are major bottlenecks in improving the performance of inverted perovskite solar cells (PSCs). Interfacial engineering for interfacial defect passivation is a promising approach for minimizing interfacial defects. In this study, the small molecule 2,6-lutidine (2,6-Lu), incorporating [6,6]-phenyl C61-butyric acid methyl ester (PCBM), was established as an electron transport layer (PCBM: 2,6-Lu ETL) to minimize charge defects at the upper interface of the perovskite. After a series of experimental tests, we confirmed that the –N– groups in 2,6-Lu could immobilize uncoordinated Pb2+ to passivate charge defects. Furthermore, the designed ETL induced a favorable energy level between the perovskite and ETL layers, boosting charge transfer and reducing charge recombination. Therefore, the inverted PSCs with the designed ETL exhibited a remarkable power conversion efficiency of 19.93 % with an outstanding long-term ambient stability of 30 d, which was ascribed to interfacial defect passivation and suitable energy level alignment.