Spectrum‐dependent photonic synapses based on 2D imine polymers for power‐efficient neuromorphic computing

Abstract 2D polymers (2DPs) have attracted increasing interests in sensors, catalysis, and gas storage applications. Furthermore, 2DPs with unique band structure and tunable photophysical properties also have immense potential for application in photonic neuromorphic computing. Here, photonic synaptic transistors based on 2DPs as the light‐tunable charge‐trapping medium are developed for the first time. The resulted organic transistors can successfully emulate common synaptic functions, including excitatory postsynaptic current, pair‐pulse facilitation, the transition of short‐term memory to long‐term memory, and dynamic filtering. Benefitting from the high photosensitivity of the 2DP, the devices can be operated under a low operating voltage of −0.1 V, and achieve an ultralow energy consumption of ~0.29 pJ per event. In addition, the heterostructure formed between the 2DP and organic semiconductor enables spectrum‐dependent synaptic responses, which facilitates the simulation of visual learning and memory processes in distinct emotional states. The underlying mechanism of spectrum‐dependent synaptic‐like behaviors is systematically validated with in situ atomic force microscopy based electrical techniques. The spectrum‐enabled tunability of synaptic behaviors further promotes the realization of optical logic functions and associative learning. This work inspires the new application of 2DPs in photonic synapses for future neuromorphic computing