Decoupling Volatile and Nonvolatile Response in Reliable Halide Perovskite Memristors

Halide perovskite is very attractive for the fabrication of energy-efficient memristors for neuromorphic applications. However, reproducibility, stability, and understanding the switching behavior still lag in comparison to other technologies. Herein, a deep-level understanding of perovskite memristors is obtained by the development of highly reproducible devices. The approach is based on a highly stable perovskite formulation (MAPbBr₃) and the use of preoxidized silver (AgI) as a buffer layer. Here, reliable perovskite memristors with device yields approaching 100%, stabilities of >10⁴ cycles for volatile response, and adequate conditions for linear potentiation/depression for nonvolatile response are demonstrated. Using these devices, the nature of the dual volatile and nonvolatile response is understood. It is shown that applying short SET voltage (V_SET) pulses leads to ion displacement inside the perovskite material with the formation of an ionic double layer close to the contacts. The displacement of the ions contributes to the series resistance of the device and to a volatile response with ions diffusing back to the perovskite at V < V_SET. Alternatively, long V_SET pulses lead to a gradual increase in current, the appearance of a chemical inductor, and a nonvolatile response. The observed nonvolatile regime is related to the formation of Ag⁺ conductive filaments.