Selective UV-Gating Organic Memtransistors with Modulable Levels of Synaptic Plasticity

Targeting the emulation of diverse synapses in the brain, organic thin-film memtransistors gated remotely by UV light are achieved and analytically modeled. They show continuously and reversibly variable device states, and the degree of the variability can also be controlled by selective UV gating. The modulable memristive characteristics cover a wide range of four orders in reading current, all with excellent state retention upon reading or power-off. The UV-gating effect stems from the UV-enhanced cumulative charge trapping/detrapping in the polymer electret layer, expressed as a linear relationship between the characteristic trapping frequency and UV power density. The organic memtransistors are utilized to successfully mimic various synapses at newborn, young, and mature stages that have different levels of synaptic plasticity, as well as the synaptic functions of paired-pulse facilitation and paired-pulse depression. The realization of versatile synaptic emulation in a single device may pave the way toward organic-based neuromorphic circuits, where UV gating could be used for remote regulation of circuit learning rate.