Dynamics of interfacial carriers and negative photoconductance in CH3NH3PbBr3-ZnO heterostructure

Understanding the interfacial charge transfer process and its dynamical mechanism is crucial to design efficient photoelectric devices. Methylammonium lead halide perovskite and zinc oxide (ZnO) have been demonstrated as promising candidates for excellent solar cells and photodetectors. However, the carrier transport process has not yet been fully explored on the perovskite surface and the perovskite/ZnO interface. Herein, a CH3NH3PbBr3-ZnO heterojunction was constructed as a quasi-phototransistor, where an apparent negative photoconductance was observed under illumination. Based on electrical and optical characterization, the photogenerated carrier transfer dynamics at CH3NH3PbBr3, ZnO, and their interface were investigated in detail. It can be assigned that the photogenerated electrons transfer toward the CH3NH3PbBr3 surface and the holes transfer to interior, so that the light-induced built-in electric field change would serve as the photogate to control the current flowing in the CH3NH3PbBr3-ZnO channel. These results provide clear images on the charge diffusion and drift process in the CH3NH3PbBr3-ZnO heterostructure. The study on the dynamics of negative photoconductivity of CH3NH3PbBr3-ZnO has great value for understanding the carrier transport properties and constructing perovskite heterostructure memory and optical switching devices.