Overcoming the Trade-off Between Efficient Electrochemical Doping and High State Retention in Electrolyte-Gated Organic Synaptic Transistors

To achieve superior device performance such as low threshold voltage Vth, high maximum on-current Ion,max, and long retention time in electrolyte-gated organic synaptic transistors, efficient electrochemical doping and high state retention are essential. However, these characteristics generally show a trade-off relationship. This work introduces an effective strategy to increase retention time while promoting efficient electrochemical doping. The approach involves blending two polymer semiconductors (PSCs) that have the same backbone but different types of side chains. Polymer synaptic transistors (PSTs) with the blend film showed the lowest Vth, highest Ion,max, longest retention time, and superior cyclic stability compared to PSTs that used films containing only one of the PSCs. The improvement in electrical and synaptic properties achieved through the blend strategy is consistently reproducible and comprehensive. It is attributed this improvement to the increased redox activity and constrained morphological changes observed in the blended PSCs during electrochemical doping, as confirmed by several electrochemical characterizations. This work is the first to increase retention time in PSTs without increasing the crystallinity of polymer film or sacrificing the electrochemical doping efficiency, which has been regarded as an unavoidable compromise in this field. This method provides an effective way to tune synaptic properties for various neuromorphic applications. Ion-gel gated polymer synaptic transistors (IGPSTs), emulating biological synapses, serve as a versatile platform for various neuromorphic applications. The blend strategy employed in this study effectively resolves the traditional trade-off between efficient electrochemical doping and high state retention in IGPSTs. Specifically, IGPSTs incorporating blended polymer semiconductors exhibit the highest maximum on-current, longest retention time, and superior cyclic stability.image