Understanding charge trapping/detrapping at the zinc oxide (ZnO)/MAPbI3 perovskite interface in the dark and under illumination using a ZnO/perovskite/ZnO test platform
We fabricated a zinc oxide (ZnO)/methylammonium lead iodide (MAPbI3) perovskite/ZnO field effect transistor (FET) test platform device through which ZnO/perovskite interfacial contact properties can be probed in the dark and under illumination. Using pulsed laser deposition, highly conductive (0.014 Ω cm) ZnO source and drain electrodes were fabricated allowing for the investigation of the interfacial charge transfer properties through current–voltage characteristics of a ZnO/perovskite/ZnO FET. With a bottom-contact FET device, gate voltage dependent current hysteresis in the drain current–gate voltage curves was probed at low temperature to minimize the effect of ion migration on electronic charge transport in the perovskite layer. Under illumination, importantly, ZnO/perovskite electrical contact properties were significantly altered due to electronic energy barrier change at the interface arising from the detrapping of electrons from the ZnO/perovskite interface, resulting in an enhanced dark current and a suppressed photocurrent. The origin of current hysteresis in the ZnO/perovskite/ZnO FET device is discussed relating it to interfacial charging/discharging associated with ultraviolet (UV)-induced oxygen adsorption/desorption. The results presented herein demonstrate that interfacial electronic properties at the donor (perovskite)/acceptor (ZnO) interface can be altered by photoinduced carrier trapping/detrapping, providing insights that UV-induced persistent photoconduction in transition metal oxide electron transport layers including ZnO may be contributing to the current hysteresis observed in the perovskite photovoltaic devices.