Inter-Ion Mutual Repulsion Control for Nonvolatile Artificial Synapse

Organic electrochemical transistors (OECTs) are promising candidates for artificial synapses to achieve high-performance synaptic characteristics. While most research has focused on modifying the properties of organic semiconductors for efficient ion doping, there is a lack of systematic investigation into the relationship between ion-mediated mechanisms and synaptic performance. In this study, an effective strategy for enhancing electrochemical doping and de-doping by utilizing different coulombic anions is proposed. The findings reveal that doped ions in the channel layer affect inter-ion interactions, influencing the non-volatile effects by improving the doping performance of the synaptic device. Moreover, electrochemical analysis indicates that ions in the channel layer are sequentially de-doped, enabling high linearity and symmetry. The fabricated devices demonstrate high-performance synaptic properties including a retention time of ≈10² s with ≈50% retention over peak current and near-ideal long-term potentiation/long-term depression (LTP/LTD) through effective electrochemical doping and de-doping. These results show that controlling both the properties of organic semiconductors and ion interactions in the electrolyte is crucial for OECTs, opening up various applications for neuromorphic computing.