Band offset measurement at the MAPbBr3/Al2O3 heterointerface by X-ray photoelectron spectroscopy

Recently, Al2O3 has been demonstrated to be an effective material type for perovskite photoelectric device performance improvement. It is therefore essential to investigate the interfacial electronic characteristics and the energy-level diagrams of perovskite/Al2O3 heterojunctions in depth. In this research, we fabricated an MAPbBr3 microcrystal/Al2O3 film heterojunction and determined the band offset by performing X-ray photoelectron spectroscopy measurements. The resulting valence band offset of ΔEv = 0.87 ± 0.01 eV and the conduction band offset of ΔEc = 3.03 ± 0.01 eV indicated occurrence of a type-I band alignment at the MAPbBr3/Al2O3 heterointerface. The carrier confinement effect was reflected in the photoluminescence spectra obtained for the heterojunction sample. This work will be valuable for optimization of the energy level alignment of perovskite/metallic oxide heterojunctions during the design of photoelectric devices.