Correspondence of Plasticity and Hysteresis in Organic Electrochemical Transistor Synapses

High Resolution Image Download MS PowerPoint Slide Organic electrochemical transistors (OECTs) display two prominent phenomena: pronounced hysteresis in transfer curves and synaptic-like plasticity under gate-voltage pulse trains. These two observations are usually analyzed with different protocols, and the direction of transfer hysteresis (clockwise/counterclockwise, CKW/CCW) is rarely used to anticipate the polarity of pulse-driven weight updates (synaptic potentiation or depression). In the context of a minimal dynamical framework built on an internal ionic state, we show that transfer-loop orientation provides an operational indicator of the sign of pulse-induced updates once the device polarity factor, pulse protocol, and operating window are fixed. More specifically, the observable response is governed by the competition between an effective ionic relaxation time and an effective electronic readout time, both defined within a stated operating window. Changing the balance between these two effective times changes the relative weight of state lag and current readout, which can switch the loop orientation and reverse the pulse response accordingly. The result is proposed not as a universal recipe with strictly constant material parameters but as a compact interpretation framework for relating fast transfer sweeps to pulse-driven plasticity under controlled OECT operating conditions.