Dual-modal artificial synapse based on a lead-free halide Cu₂AgBiI₆ for image processing and information encryption

The lead-free perovskite-inspired materials are regarded as one of the alternatives to lead-based perovskite for the preparation of neuromorphic devices due to their low toxicity, excellent optical and transport properties. Herein, a two-terminal artificial synapse was fabricated based on a novel lead-free halide Cu₂AgBiI₆ thin film. The fabricated device exhibited the versatile synaptic behavior whether subjected to external electrical or optical stimulation benefitting from the excellent photoelectric characteristics of Cu₂AgBiI₆. Furthermore, the intrinsic photovoltaic feature of Cu₂AgBiI₆ enabled the device with capabilities of operating in a self-powered mode under optical stimulation. The device successfully imitated the retina's capacity for color perception by employing optical pulses of various wavelengths. The dependence of the device response on the optical pulse frequency allowed it to function as a high-pass filter for image sharpening. At last, the device was applied for the information encryption and decryption transmission based on a constructed password book including 128 common characters and numbers, which shows great potential for information encryption and decryption transmission. The comprehensive characters of the device display great superiority over other artificial synaptic devices.