New Impedance Model for OECTs

Currently there exists a critical lack in understanding how electrolyte concentration affects OECT performance. Though traditional capacitance voltage division theory is frequently used to describe OECT characteristics, some properties cannot be fully explained especially in AC operation. We propose a new impedance-based model incorporating both capacitive coupling and resistive voltage division across the electrolyte to explain these effects. Our model successfully predicts and verifies a frequency-dependent threshold voltage shift under high-frequency signals. Leveraging this insight, we demonstrate that appropriately increasing the gate DC bias compensates for this shift, thereby enhancing transconductance in high-frequency applications.

In our new publication, “Beyond Capacitance Ratio: Electrolyte Voltage Division and a New Impedance Model for OECTs”, we propose a novel impedance-based model incorporating both capacitive coupling and resistive voltage division across the electrolyte to explain these effects. Our model successfully predicts and verifies a frequency-dependent threshold voltage shift under high-frequency signals. Leveraging this insight, we demonstrate that appropriately increasing the gate DC bias compensates for this shift, thereby enhancing transconductance in high-frequency applications.

The study was carried out by Qinyu Hu as part of his PhD research and was made possible through the continuous support and contributions of all co-authors. We gratefully acknowledge the Helmholtz Nano Facility for providing the cleanroom environment for organic electrochemical transistor fabrication.

Publication: Hu, Q., Li, H., Sun, S., Montes, V. R., Ingebrandt, S., Santoro, F., Offenhäusser A., & Mayer, D. (2026). Beyond Capacitance Ratio: Electrolyte Voltage Division and a New Impedance Model for Organic Electrochemical Transistors. ACS Applied Materials & Interfaces. https://doi.org/10.1021/acsami.6c09414

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