Energy‐Level Modulation in Diboron‐Modified SnO₂ for High‐Efficiency Perovskite Solar Cells

Abstract

Energy‐level modulation between perovskite and carrier transport layers to obtain a promoted carrier extraction and reduced charge recombination is an effective way to achieve high‐efficiency perovskite solar cells. Here, diboron is used as an effective interfacial modifier between SnO 2 and perovskite. By taking advantage of the higher Fermi level on the surface of SnO 2 after diboron treatment, a power‐conversion efficiency of 22.04% in a solar cell device based on two‐step solution‐processed planar n‐i‐p structure is obtained. With the help of thorough characterizations, it is argued that the diboron‐treated SnO 2 exhibits some Sn 3+ species, which serve as electron donors with a more n‐type nature, promoting electron extraction and reducing carrier recombination in the electron transport layer (ETL)/perovskite interface. Further analysis speculates that the formation of surface diboron–oxygen Lewis pair induces a reducing state of diboron complexes, resulting in the spontaneous electron redistribution and the formation of Sn 3+ −O –• species. This provides an effective chemical approach to tune the energy alignment between the oxide ETL and absorber.