Multifunctional Two-Terminal Optoelectronic Synapse Based on an Organic Semiconductor Film

Organic materials show great potential in the fields of biomimetics and neuromorphic computing due to their molecular diversity, cost-effective manufacturing processes, unique optical and chemical properties, and remarkable mechanical flexibility. In this work, an optoelectronic synaptic device based on the organic semiconductor poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl))thieno[3,2b]thiophene] (DPPDTT) is fabricated by a simple solution process. The fabricated device successfully emulates typical functions of biological synapses, including excitatory postsynaptic current, pair-pulse facilitation, the conversion of short-term memory to long-term memory, and “learning experience” behavior by modulating light stimuli. Furthermore, the light logic functions of “AND” and “OR” are realized by using light pulses with different wavelengths, as well as the simulation of associative learning. Moreover, a flexible device was fabricated on a PET substrate, which not only exhibits good synaptic performance but also demonstrates excellent bending stability. Eventually, through the simulation based on a convolutional neural network algorithm, our device successfully realizes the high-precision recognition of handwritten digital even after bending 1000 times. This work showcases a promising methodology for developing brain-inspired flexible optoelectronic synapses for future neural computing networks based on organic materials.