Revealing the Effect of Substantial A Site Cation Multiplicity in Lead-Free Double Perovskites for Memristor-Based Synaptic Devices

In the realm of memory storage and brain-inspired neural computing, memristors stand out as some of the most rapidly advancing electronic components. In this aspect, Halide perovskite-based two-terminal memristors have gained widespread usage in energy-efficient artificial synapses and resistive random-access memory systems. Their appeal lies in their lower operating voltage, high ON/OFF ratio, cost-effective production, and reliable photoelectric regulation performance. In this study, we have successfully harnessed a one-step chemical synthesis method to fabricate a series of lead-free double perovskite ((Cs_1-<i>x</i>Rb_<i>x</i>)₂AgBiBr₆, <i>x</i> = 0,0.1,0.15). While the pure Cs₂AgBiBr₆ device lacked discernible switching characteristics, introducing Rb dopants resulted in robust resistive switching attributed to defect states from the Cs site Rb substitution. Dopant concentration is tailored to enhance device performance─durability, reproducibility, mechanical flexibility, and ON/OFF ratio. Additionally, we confirmed the valence change mechanism through temperature-dependent conductivity of the high resistive states and SET/RESET voltage analysis. Remarkably, resistance of flexible memory devices remains unaffected by bending curvature. Furthermore, our two-terminal synaptic device effectively regulates voltage pulses, mimicking biological synapses. Pulse measurements emulate fundamental synaptic functions: excitatory postsynaptic current, paired-pulse facilitation, long-term potentiation, and long-term depression under normal conditions. When applied to handwritten digit recognition simulation, these synaptic memristors achieved a high accuracy rate of 96.6%. These findings hold promise for next-gen electronics with lead-free Rb-doped double perovskite-based artificial synapses.