Investigation of Electrochemical Transport, Gate Leakage, and Transconductance Behavior in PEDOT:PSS Organic Electrochemical Transistors

Organic Electrochemical Transistors (OECTs) are promising candidates for low-voltage bioelectronic systems due to their high transconductance, mixed ionic–electronic transport, and compatibility with flexible substrates. In this work, we investigate the electrochemical transport, gate leakage, and transconductance behavior of screen-printed PEDOT:PSS OECTs, with emphasis on the relationship between ionic coupling and output characteristics. Key electrical and electrochemical parameters—including drain current modulation, transconductance evolution, gate current behavior, and capacitance–voltage response—were systematically analyzed to elucidate the mechanisms governing device operation. The results reveal clear trade-offs between parasitic resistance, volumetric electrochemical capacitance, and effective gate control, which in turn influence signal integrity and amplification efficiency. Devices exhibiting reduced parasitic effects demonstrated lower gate leakage, improved signal-to-noise ratio, and more stable transconductance, whereas devices with stronger ionic coupling showed enhanced drain current at the expense of nonlinearity in the saturation regime. High-frequency C–V measurements and gate-current modeling further confirm distinct electrochemical dynamics driven by modulation of mixed conduction pathways. These insights provide a deeper understanding of OECT operation and offer practical guidelines for optimizing device architecture in solid-state and flexible bioelectronic applications.