Lead-free, highly-stable methyl ammonium bismuth halide perovskite memristors for mimicking biological synapses

Abstract

In this work, lead-free and non-toxic (CH3NH3)3Bi2I9 (abbreviated as MABI) films are synthesized using a two-step sol-gel method, and FTO/MABI/Ag memristors are fabricated based on MABI films. The memristive behaviors in the devices were studied, showing controllable resistance change under voltage sweeps as well as pulses. The memristors are capable of mimicking the plasticity of biological synapses by setting pulse parameters, such as paired pulse facilitation (PPF), long-term plasticity, spike-timing-dependent plasticity (STDP), spike-rate-dependent plasticity (SRDP), and spike-number-dependent plasticity (SNDP). Moreover, the cycle of “learning-forgetting-relearning” typically observed in human learning can be also realized by the memristor. Based on study of current conduction behavior and the influence of top electrodes on I–V hysteresis in the memristors, it is concluded that the formation and rupture of conductive filaments formed by iodine vacancies in the MABI films are responsible for memristive characteristics. The MABI film and FTO/MABI/Ag memristor demonstrated good stability in a three-month test conducted in ambient air. The lead-free, non-toxic, and stable MABI-based memristors can be used promisingly for neuromorphic computing and machine learning in the future.