Organic electrochemical transistors (OECTs) combine ionic charging of a mixed ionic–electronic channel with electronic current transport, giving rise to transient switching, transfer hysteresis, and synaptic-like responses. However, these phenomena are often studied separately, obscuring their common physical origin and their distinction from memristive behaviour. Here, we establish a unified interpretation of OECT dynamics based on delayed ionic channel charging and its electronic readout.

Using PEDOT OECTs under gate-voltage steps, we show that gate-current transients exhibit a nearly drain-bias-independent decay, enabling extraction of an ionic diffusion time of approximately 30–40 ms. In contrast, the drain-current transient changes strongly with drain-bias magnitude and polarity, reflecting the contribution of lateral electronic transport to the readout of the same ionic charging process. Despite their different temporal morphologies, the characteristic decay times extracted from gate and drain currents remain consistent, confirming vertical ionic diffusion as the intrinsic timescale governing channel charging. [1]

Building on this separation between ionic relaxation and electronic readout, we relate transfer-curve hysteresis to pulse-driven synaptic plasticity within a reduced diffusion–transport model. For a fixed device polarity, operating window, and pulse protocol, the orientation of the transfer loop provides an operational indicator of whether repeated pulses produce potentiation or depression. Both observables arise from the delayed evolution of the same ionic state, while their measured sign is determined by the competition between ionic relaxation and electronic readout timescales. [2]

Finally, comparison with a conductance-activated memristor clarifies that similar pulse-to-pulse current accumulation does not imply the same memory variable. In memristors, the internal state directly controls conductance; in OECTs, the evolving state is reversible channel charging. Consequently, conventional OECT potentiation is intrinsically volatile in the long-time limit unless an additional retained redox, ionic, trapping, or material state is introduced. This framework connects transient response, hysteresis, and neuromorphic function while defining the physical boundary between charging-based transistor dynamics and conductance-state memory.