Ions and Defects at Interfaces Control the Polarity of Resistive Switching in Perovskite-based Memristors

A memristor is a two-terminal electronic component that modify its conductance state depending on how much charge has passed through it previously. Halide perovskites are materials recently employed for neuromorphic computing in this type of resistive switches. Their performance is rapidly improving, yet the activation and deactivation mechanisms remain poorly understood. For instance, a change in the perovskite formulation can induce activation at either positive or negative polarity. By fixing the device configuration, we show that MAPbI₃ conductance activates at positive voltages, while the bromide derivative, MAPbBr₃, conductance activates at negative potentials. We attribute this behavior to a high concentration of defects at the perovskite/external interface in the pristine device. Subsequently, we generate two device configurations in which there is an excess of iodide ions at either the top or the bottom interface. In particular, we introduce an interfacial layer based on a blend of polyethylene glycol and ionic liquid. The buffer layer, placed at either the top or bottom electrode, modulates the activation/deactivation quadrant, confirming that halide defect migration at the contacts initially drives the memory response. Overall, the current work provides valuable information to design more efficient memristor devices.