Organic Photonic Synaptic Devices with UV-Stimulated Inhibition and Adaptive Short-Term Plasticity

Bidirectional modulation of synaptic weight lays the basis for learning and memory in the brain, and the development of brain-inspired photonic synaptic devices is hindered by deficient light-stimulated inhibition. In this report, a type of organic thin film neuromorphic devices with a planar two-terminal architecture, featuring as the inhibitory regulation of synaptic weight over two orders of magnitude upon selective UV illumination is developed. The in situ monitoring on the floating electrode potential and the corresponding simulation results demonstrate the effect of cumulative hole trapping in the polymer electret layer, which modulates the device conductance in a nonvolatile manner. Remarkably, UV-induced long-term depression is accompanied by enhanced short-term potentiation in the device that may preserve a stable level of total synaptic activities. The UV-stimulated inhibition and the adaptive short-term plasticity, as well as the ON and OFF responses to light in the organic photonic synaptic device, suggest its potential applications in photonic neuromorphic computing.