Dual-liquid-gated electrochemical transistor and its neuromorphic behaviors

Highlights: • A dual-liquid-gated OECT offers a post-fabrication and facile tuning method to tune critical electrical parameters. • Mathematical analysis was developed to demonstrate the electrochemical doping/de-doping mechanism. • Paired-pulse depression and decay time were successfully controlled by varying the auxiliary-gate bias. Organic electrochemical transistors (OECTs) are attracting great interest in the field of bioelectronics due to their low operating voltage, flexibility, and biocompatibility. Tunability of the static and transient characteristics renders OECTs with flexible electrical responses and versatile functionalities. However, existing tuning methods are known by changing the structure or composition of OECTs, which are empirical due to the lack of accurate structure-function relationships. Here, we report a post-fabrication and facile tuning method by using a dual-liquid-gate configuration. Based on this, critical parameters of OECT, e.g., threshold voltage (V_TH), gate bias for the peak transconductance (V_G(g*_m)), electric hysteresis (V_hys), minimum of the subthreshold swing (SS*), and response time (τ), can be readily tuned over a range of 0.52 V, 0.48 V, 0.20 V, 0.38 V/decade and 7.2 ms, respectively. We have also developed corresponding mathematical analyses based on the dual-liquid-gating process. Detailed studies on the transient electrical properties demonstrate that auxiliary-gate biases influence the electrochemical doping/de-doping state of the semiconducting channel during the main-gate bias sweeping. Furthermore, typical neuromorphic behaviors of paired-pulse depression and decay time were successfully controlled by varying the auxiliary-gate bias. The proposed dual-liquid-gating is ready for precise engineering on OECT, which is beneficial as an effective tool for conducting an in-depth theoretical study on OECT, constructing multifunctional sensors, and developing more plasticizable neuromorphic devices.