Programming Neuromorphic Plasticity Through Ionic and Electronic Coupling in Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) encode the history of ionic motion as persistent changes in channel conductance, providing a material basis for neuromorphic plasticity. Yet memory lifetime is determined not simply by electrochemical doping, but by how the programmed ionic and electronic state relaxes or stabilizes after stimulation. This Review establishes a mechanistic framework that classifies OECT responses as rapidly relaxing, metastably confined, or persistently stabilized states. We show how semiconductor chemistry and morphology, electrolyte composition and ion identity, interfacial interactions, and device architecture collectively govern ion injection, transport, confinement, and release. These processes are connected to temporal processing, selective consolidation, and persistent synaptic weight storage. We further assess the coupled tradeoffs among programming speed, retention, reversibility, update linearity, and endurance. Rather than maximizing retention alone, we identify function matched and reversible stabilization, together with its decoupling from programming kinetics and weight update characteristics, as a central design principle for neuromorphic OECTs.