Regulating the electrode potential offset in perovskite solar cells for boosting interfacial charge transfer

In perovskite solar cells (PSCs), the interfacial charge transfer is adjusted by a band offset to improve the device performance. However, the band offset cannot explain some abnormal phenomena of interfacial charge transfer. In this study, we adjusted the electrode potential offset (ΔEPO) at the perovskite/hole transport layer (HTL) interface by employing different side chain HTLs, which increased the device efficiency from 0.6% to 18.1%. We also investigated the relationship between chemical reaction kinetics at the perovskite/HTL interface and the ΔEPO by in situ FTIR, NMR, theoretical calculations and electrochemical measurements. Accordingly, we proposed ΔEPO as a driving force descriptor for interfacial charge transfer in PSCs for the first time. These results deepen the understanding of the interfacial charge transfer and offer a new design principle for the interface in the PSCs.