DUAL-SIGNAL ORGANIC ELECTROCHEMICAL PHOTODETECTOR

Organic electrochemical transistors (OECTs) are widely explored for biosensing applications, yet their use as photodetectors remains underdeveloped. In this study, we report the photoresponse of an OECT incorporating a poly(3-hexylthiophene) (P3HT) channel, operated in a two-terminal configuration with the gate and source electrodes electrically shorted. The device exhibited diode-like behavior with asymmetric drain current (Id) characteristics under forward and reverse drain-source voltage (Vds) sweeps. Upon light illumination, both Id and the gate current (Ig) increased, with notably higher gain observed in the depleted regime at negative Vds. Specifically, the Id gain reached ~1.6, while Ig showed a gain exceeding 8 under illumination at –0.3 V. These results indicate that light-induced modulation of interfacial doping governs the device behavior. The simultaneous sensitivity of both drain current (Id) and gate current (Ig) to illumination enables the development of organic electrochemical transistor (OECT)-based dual-parameter photodetectors, particularly suited for applications demanding soft, low-power, and easily integrable light sensors. Keywords: Organic electrochemical transistor, photodetectors, P3HT, active channel material, drain source voltage, gate current.