Unraveling the Electrochemical Electrode Coupling in Integrated Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) have gained enormous attention due to their potential for bioelectronics and neuromorphic computing. However, their implementation into real-world applications is still impeded by a lack of understanding of the complex operation of integrated OECTs. This study, for the first time, elaborates on a peculiar behavior that integrated OECTs exhibit due to their electrolytic environment-the electrochemical electrode coupling (EEC), which has severe implications on the device and circuit performance, causing a loss of output saturation and a threshold voltage roll-off. After developing a physical model to describe this effect, it is substantiated with experimental data, and the crucial role of the gate electrode is discussed. Furthermore, the impact of the electrode/channel overlap on the saturation in the output curve is evaluated. It is then investigated how its detrimental effect on circuit performance can be minimized, and the optimization of a simple logic gate is demonstrated. This study has fundamental implications for researchers exploring materials and device architectures for OECTs and for engineers designing integrated OECT-based circuits.