Organic lateral electronic synapse with history-dependent metaplasticity

Abstract A solution-processed polymer thin film memristor is developed and utilized as a lateral electronic synapse. Such an organic synaptic device can progressively modulate its lateral conductance in response to afferent voltage pulses, based on the ion redistribution mechanism that empowers the spatiotemporally correlated electrochemical doping in the poly(3-hexylthiophene-2,5-diyl) active layer. This intriguing device is harnessed to mimic synaptic metaplasticity, manifested as two distinct stages under the same voltage pulse stimulation. In the early stage of the stimulation, the device shows weak synaptic plasticity in the current range of 0.1–100 nA. In the late stage, it transforms into strong synaptic plasticity above the threshold current of 100 nA. The transition process is visible benefiting from the electrochromic feature of the polymer thin film. Remarkably, the threshold between the two stages is adjustable depending on the manner of voltage pulse stimulation, evoking the stage transition either by just a few strong stimuli or by more than a dozen weak stimuli. The metaplasticity behavior endows the electronic synapse with great potential to emulate sophisticated synaptic functions.