Spectrally Selective Bipolar Self‐Powered Opto‐Synaptic Responses in Tandem 2D van Der Waals Ferroelectric Heterojunctions

Human vision converts incident light directly into electrical signals without external power, enabling autonomous sensing, retinal preprocessing, neuronal transmission, and adaptive learning with intrinsic memory erasure. Inspired by this capability, we report a spectrally selective bipolar opto‐synaptic device based on a tandem α‐In 2 Se 3 /CuInP 2 S 6 (CIPS)/black phosphorus (BP) 2D van der Waals ferroelectric heterojunction that operates exclusively under optical stimulation. The device exhibits opposite open‐circuit voltage and short‐circuit current polarities under visible and near‐infrared (NIR) illumination, closely emulating excitatory and inhibitory synaptic responses as well as ON/OFF bipolar cell signaling in the human retina. Strong opto‐ferroelectric coupling and oppositely oriented interfacial built‐in potentials at the α‐In 2 Se 3 /CIPS and CIPS/BP heterojunctions enable spectral‐selective discrimination, retinal‐like motion detection, visible‐light adaptation, and fully optical memory writing and erasing. As a self‐powered optoelectronic synapse, the device demonstrates pronounced paired‐pulse facilitation (≈152%), a transition from short‐ to long‐term memory, and bidirectional conductance modulation under repeated visible and NIR stimuli. Artificial neural network simulations and real‐time pattern recognition achieve an accuracy of ≈91%. Additionally, fully optical logic operations, including AND, OR, NAND, NOR, and NOT gates, are realized. This work establishes a versatile platform for energy‐efficient, adaptive, and human‐like artificial vision systems integrating neuromorphic computing and intelligent imaging.