A DC Compact Model of an Organic Electrochemical Transistor Based on a Semiconductor Physics and Thermodynamic Approach

Recent progress in printable electronics and biointerfaces has driven a growing interest in organic electronics for biosensor and neuromorphic applications, offering a valuable complement to traditional silicon technologies. Among organic electronics, organic electrochemical transistors (OECTs) have garnered significant attention for their high transconductance, biocompatibility, and dual ionic‒electronic charge transport capabilities. While OECTs show strong promise, their variability due to fabrication and material inconsistencies, limited insight into charge transport, and absence of standard models hinder their integration. A robust, physics‐based compact model can bridge these gaps and facilitate broader adoption of this device technology. This work presents a physics‐based DC compact model for OECTs, integrating electrochemical interactions using the Nernst equation in the above threshold regime with drain bias‐dependent diffusive charge transport in the subthreshold regime, unified by a hyperbolic tangent transition. It integrates the threshold voltage roll‐off effect and the drain voltage‐dependence of the hole mobility using the Poole‒Frenkel mobility model. The model is validated against experimental data from four distinct geometries of p‐type poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT: PSS) OECTs, which show excellent agreement with the measurements. The model reliably captures DC characteristics, making it suitable for incorporation into circuit simulation tools to support broader application development.