Artificial Synapse Based on a δ-FAPbI₃/Atomic-Layer-Deposited SnO₂ Bilayer Memristor

Halide perovskite-based resistive switching memory (memristor) has potential in an artificial synapse. However, an abrupt switch behavior observed for a formamidinium lead triiodide (FAPbI₃)-based memristor is undesirable for an artificial synapse. Here, we report on the δ-FAPbI₃/atomic-layer-deposited (ALD)-SnO₂ bilayer memristor for gradual analogue resistive switching. In comparison to a single-layer δ-FAPbI₃ memristor, the heterojunction δ-FAPbI₃/ALD-SnO₂ bilayer effectively reduces the current level in the high-resistance state. The analog resistive switching characteristics of δ-FAPbI₃/ALD-SnO₂ demonstrate exceptional linearity and potentiation/depression performance, resembling an artificial synapse for neuromorphic computing. The nonlinearity of long-term potentiation and long-term depression is notably decreased from 12.26 to 0.60 and from -8.79 to -3.47, respectively. Moreover, the δ-FAPbI₃/ALD-SnO₂ bilayer achieves a recognition rate of ≤94.04% based on the modified National Institute of Standards and Technology database (MNIST), establishing its potential in an efficient artificial synapse.