Ferroelectric–Electrolyte Hybrid Gate Dielectrics for Organic Synaptic Transistors with Long‐Term Plasticity

ABSTRACT Organic electrochemical transistors (OECTs) have been of tremendous interest for neuromorphic memories thanks to their excellent device uniformity, facile processibility and biocompatibility. One of the hurdles for precise emulation of synaptic functions is poor long‐term plasticity, mainly originated by facile diffusion of mobile ions between a channel and an electrolyte gate dielectric. Herein, we present that a gate dielectric of ferroelectric poly(vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)], blended with an ionic liquid of 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM][TFSI]), is beneficial for enhancing long‐term plasticity for OECTs. Comparative studies for P(VDF‐TrFE) and nonferroelectric fluorinated polymers indicate that polar ferroelectric β ‐phase crystals assist regulation of mobile ions in a nonvolatile manner, leading to a large memory window with an ON/OFF drain current ratio of ∼10 3 . The ferroelectric OECT exhibits long‐term potentiation (LTP) and long‐term depression (LTD) characteristics, and long‐term retention time of >10 3 s with distinguishable synaptic weight states. Our strategy provides a simple route for emulation of long‐term synaptic behavior, potentially applicable for diverse sort of electrochemical synapses.