Threshold Resistive Switching in Inorganic Lead-Free Cesium-Bismuth Iodide Perovskite for Neuron Emulation

High-performance halide-based perovskite memory devices have been developed, exhibiting a variety of synaptic and neuronal functions based on nonvolatile and volatile or threshold switching memristors, respectively, compatible with low power consumption. However, the key ingredient in these perovskite-based systems is the presence of highly toxic lead, which hinders their further development and commercial use. A lead-free perovskite approach for memristive applications could enable sustainable devices, opening the path for practical applications. Herein, we report on the fabrication and characterization of a threshold resistive switching device using solution-based manufacturing, based on a lead-free, all-inorganic perovskite, namely cesium-bismuth iodide (Cs₃Bi₂I₉) perovskite. The memristive device exhibits threshold switching current-voltage (I-V) characteristics with an ON/OFF ratio of >10⁴, while operating in the 0 V-5 V range and exhibiting a cycling endurance of 650 cycles with reproducible behavior. Furthermore, linear long-term, threshold-dependent potentiation protocols, accompanied by abrupt resistance suppression under depression protocols, are demonstrated. The volatile nature of memristive switching allowed the implementation of current spiking activation, similar to neuron spiking protocols, thus opening the path for neuronal emulation. These results can further advance the development of environmentally friendly perovskite memory systems for neuromorphic computing applications, providing a cost-effective alternative to oxide-based devices.