Charge transfer enhancement of TiO2/perovskite interface in perovskite solar cells

In the conventional perovskite solar cells (PSCs) structure, TiO2 is the most commonly used electron transport layer (ETL) as it has good energy-level matching with perovskite layer. However, oxygen vacancy defects will appear when TiO2 is exposed to ultraviolet light for a long time, which would reduce its carrier extraction ability. Here, we report a simple and effective interface engineering method for TiO2 ETL to achieve a highly efficient PSCs. An ultra-thin [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) layer is used to modify the mesoporous TiO2/perovskite layer interface. The PCBM effectively passivates defects on the TiO2 surface, promotes the extraction of electrons, and improves the quality of the perovskite film. Finally, a high efficiency of 16.4% was achieved for the modified device, much higher than 13.5% of the reference devices. After storing for 12 days in an atmosphere with an air humidity of 30 ± 5%, the efficiency of the PSCs maintains more than 60% of its initial level. This strategy is beneficial to enhance the efficiency and working stability of PSCs.