Size and Surface Chemistry Effects on the Synaptic Behavior of Halide Perovskite Thin Films

Halide perovskites are promising for energy-efficient and reconfigurable artificial synapses due to the unique charge transport characteristic, i.e., ionic-electronic coupling. This work attempts to detangle the size and surface chemistry effects on perovskite-based synaptic memristors that remain elusive to date. Herein, three different perovskite-based memristors were constructed for mimicking the synaptic behavior: device 1 based on CsPbBr₃-nanocrystal (NC) film terminated with short alky ligands, device 2 based on naked CsPbBr₃-NC film, and device 3 based on CsPbBr₃ bulk film. In addition to emulating a series of essential synaptic functions, our results suggest that perovskite-NC films outperform their bulk counterpart in light of paired pulse facilitation (PPF) index and gain due to an increased trap density and enhanced ion transport. The incorporation of short alkyl ligands into the NC surface decreases the film conductance without suppression of charge transport, thereby reducing the on-state energy consumption. Using the best-performed NC device comprising a neuron network, we did a preliminary proof-of-concept demonstration of the potential for brain-inspired neuromorphic computing which was proved effective for digit recognition with a high accuracy of 94%. Our study signifies the importance of grain size and surface chemistry engineering for the development of high-performance robust synaptic memristors based on halide perovskites.