All-optically controlled photoelectrochemical synapse for aqueous neuromorphic applications.

Aqueous optoelectronic synapses analogous to the biological nervous system offer versatile advantages such as low energy consumption and high parallelism. All-optically controlled bidirectional photoresponsive optoelectronic synapses play a crucial role in the realization of bioinspired neuromorphic systems. However, mainstream all-optically controlled optoelectronic synapses based on solid-state devices operate in non-aqueous environments, restricting their application in aqueous neuromorphic engineering. This study proposes a two-terminal all-optically controlled self-powered photoelectrochemical optoelectronic synaptic device based on MOF-derived In₂O₃/CuO heterojunctions operating in an aqueous electrolytic medium. Leveraging oxygen vacancy and wavelength-dependent interfacial carrier transfer competition, bidirectional modulation of versatile synaptic excitatory and inhibitory behaviors is achieved within a single photoelectrochemical optoelectronic synapse under two distinct wavelengths of optical pulse irradiation (365 and 450 nm). Furthermore, the all-optically driven device not only performs five fundamental Boolean logic operations ("OR", "AND", "XOR", "NOR", and "NAND") but also implements handwritten digit recognition via an artificial neural network, achieving an accuracy exceeding 93%. This work provides a novel insight into the development of high-performance, low-power, all-optically controlled aqueous neuromorphic optoelectronic synapses.