Proceedings of MATSUS Spring 2024 Conference (MATSUS24)
DOI: https://doi.org/10.29363/nanoge.matsus.2024.073
Publication date: 18th December 2023
Organic electrochemical transistors (OECTs) prove to be effective devices in various applications such as neuromorphic functionalities, bioelectronics, and sensors. Analyzing these mixed ionic-electronic devices is often complex due to the coupling of hole transport along the channel with ion insertion from the electrolyte. Numerous literature reports highlight persistent dynamical hysteresis effects in current-voltage curves, attributed to the gradual ionic charging of the channel under applied gate voltage.
We introduce a model that takes into account the primary electrical and electrochemical operational aspects of the device. This model is based on a thermodynamic function of ion insertion, allowing for the convenient classification of hysteresis effects. Such hysteresis can be categorized as capacitive or inductive. We specifically identify the volume capacitance as the derivative of the thermodynamic function, linked to the chemical capacitance of the ionic-electronic film.
Our findings reveal that the inductor response observed in impedance spectroscopy is associated with ionic diffusion from the surface, filling the channel up to the equilibrium value. The model uncovers multiple dynamical features tied to specific kinetic relaxations that govern the transient and impedance response of the OECT.
This work is funded by the project PID2022-141850OB-C21/AEI/10.13039/501100011033/FEDER, EU.