Self-Powered\nand Broadband Optical Synapse Device\nBased on Se-Vacancy Bi<sub>2</sub>O<sub>2</sub>Se for Artificial Vision\nSystem Application

The optical synaptic devices, inspired by the human visual\nsystem\nand capable of emulating biological synaptic behaviors, have demonstrated\nsignificant potential for artificial vision applications. However,\ncontemporary optical synaptic devices are hindered by several limitations,\nincluding a narrow response range, intricate structures, compromised\nstability, and substantial energy demands. Herein, large single-crystal\nBi<sub>2</sub>O<sub>2</sub>Se nanosheets with selenium vacancies (Bi<sub>2</sub>O<sub>2</sub>Se–V<sub>Se</sub>) were synthesized via\nphysical vapor deposition. Based on the Bi<sub>2</sub>O<sub>2</sub>Se–V<sub>Se</sub> nanosheet, a self-powered, broadband optical\nsynaptic device was developed simply by a straightforward asymmetric\ncontact approach. The device proficiently replicates synaptic functionalities\nwithout any electrical power requirement. Furthermore, an artificial\nvision system comprising a 5 × 5 array of self-powered optical\nsynaptic devices was constructed. Under illumination at wavelengths\nof 350, 532, and 1050 nm for 100 s, the intensity of the image pattern\ncan be kept at a high memory level of 94.91%, 44.92%, and 12.83% after\nattenuation of 100 s, which demonstrates the excellent image sensing,\nlearning, and memory storage properties. This research paves the way\nfor further exploration of optical synaptic devices and contributes\nnovel insights into the development of artificial vision systems.