Improving ion uptake in artificial synapses through facilitated diffusion mechanisms

Several studies have explored ways to enhance the interaction between the channel layer and ions to realize artificial synapses using organic electrochemical transistors (OECTs). The attachment of glycol side chains can remarkably enhance the ion transport to improve nonvolatile properties via polar groups; however, a comprehensive and methodical evaluation of this phenomenon has yet to be conducted. In this study, we observed the reactivity toward ions and the doping mechanism that changes by glycol group substitution to the side chains of DPP polymers. The analysis revealed that in the presence of glycol chains, the doping mechanism changes to diffusion-dominated, which allows ions to penetrate the channel and interact with it more intensely, thereby enhancing synaptic performance. The fabricated devices successfully mimicked the behavior of biological synapses, such as good long-term synaptic plasticity (LTP), paired-pulse facilitation (PPF), and long-term potentiation/depression (LTP/D). Based on these properties, a high accuracy of 93.7% has been achieved in an artificial neural network for handwritten data recognition at the Modified national institute of standards and technology (MNIST). These findings provide new insights for the realization of artificial synapses and could inspire other research involving reactions with ions.