Artificial synapse using flexible and air-stable Cs₃Bi₂I₉ perovskite memristors

Abstract Von Neumann bottleneck necessitates the creation of dedicated processors for neuromorphic artificial intelligence tasks such as in-memory computing, where memristors are formulated as synapses. Perovskites are great candidates for memristors owing to their mixed ionic–electronic conduction and their compatibility with cost-effective processing techniques. In this work, we have fabricated a highly stable, lead-free, and flexible perovskite memristors by e-beam evaporation of hot-pressed zero-dimensional (0D) Cs 3 Bi 2 I 9 pellets. These memristors exhibit reproducible bipolar resistive switching with low operating voltages of −0.18 V and 0.26 V, an excellent ON/OFF ratio (>10 5 ), and high endurance (>10 4 cycles). They were air-stable for more than 30d and were repeatedly tested under high humidity (>80%) atmospheric conditions without encapsulation. The resistive switching in these devices persists even under applied mechanical stress up to a bending radius of 5 mm. A 4 × 4 crossbar array of these Cs 3 Bi 2 I 9 memristors has been fabricated, which gave a device yield of 81%. Furthermore, their potential for use as artificial synapses has been demonstrated by obtaining critical neuromorphic characteristics such as spike duration dependent plasticity, paired pulse facilitation, and long-term plasticity. This work also shows that 0D Cs 3 Bi 2 I 9 memristors have the potential to mimic biological synaptic functions of learning and forgetting, which may be useful in realizing flexible and low-power neuromorphic circuits in the near future.