Enhancing Synaptic Plasticity and Multistate Retention of Organic Neuromorphic Devices Using Anion‐Excessive Gel Electrolyte

Abstract Recently, organic electrochemical transistor (OECT)‐based neuromorphic devices have attracted considerable attention due to their diverse advantages such as ionic‐electronic coupling, low voltage operation, gradual and tunable conductance change, mechanical flexibility, and biocompatibility. However, for practical implementation in artificial neural networks (ANNs), key issues such as limited long‐term plasticity (LTP) and weak multistate retention need to be addressed. These challenges mainly stem from the disruption of electrical equilibrium of the electrolyte due to the penetration of ions into the active layer. Here, anion‐excessive gel‐based organic synaptic transistors (AEG‐OSTs) using an electrolyte containing both molecular dopant and ionic liquid/salt are developed to overcome these limitations. AEG‐OSTs exhibit greatly enhanced LTP characteristics and multistate retention, compared with conventional ion gel‐based OSTs (CIG‐OSTs). This significant advancement stems from a novel electrolyte design using an anion‐excessive gel. This gel introduces a “charge buffering” mechanism that mitigates the disruption of electrical neutrality after electrochemical doping, overcoming a fundamental bottleneck that has previously limited OECT‐based neuromorphic devices. A simulation based on handwritten digits exhibits greater recognition accuracy (95.48%) than CIG‐OSTs (88.95%), reaching the ideal case (95.82%). These results demonstrate the high potential of AEG‐OSTs as an efficient platform for OECT‐based neuromorphic devices.