Interfacial defects passivation and energy level alignment with small molecule pyridine material for efficient and stable inverted perovskite solar cells

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.