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Spray-Coated Melanin/PEDOT:PSS Films for Sustainable Organic Electrochemical Transistors
Published on: October 28, 2025
Ion-backbone accessibility enables unity doping efficiency in organic electrochemical transistors.
Won Jun Pyo1,2, Kyeong-Jun Jeong3,4, Jordan Shanahan2
1Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea.
Nature Communications
|July 14, 2026
Summary
A new metric, effective volumetric capacitance, reveals that optimizing charge carrier density, not just ion uptake, enhances organic electrochemical transistors. This finding guides the design of high-performance organic electronics.
Area of Science:
- Materials Science
- Organic Electronics
- Electrochemistry
Background:
- Volumetric capacitance (C*) is a common metric for organic electrochemical transistors.
- C* does not differentiate between Faradaic and non-Faradaic processes, limiting its ability to quantify active charge carriers.
- This limits understanding of doping capacity in organic electronic devices.
Purpose of the Study:
- Introduce effective volumetric capacitance (Ceff* = C* · η) as a metric for electronically effective volumetric doping.
- Quantify the role of doping efficiency (η) in device performance.
- Establish a design rule for organic mixed conductors.
Main Methods:
- Developed and applied the effective volumetric capacitance metric.
- Investigated the impact of ionophilic side chains on ionic uptake and doping efficiency.
- Analyzed the effect of side-chain removal on ion access and doping efficiency.
- Fabricated and characterized organic electrochemical transistors.
Main Results:
- Ionophilic side chains increase ionic uptake but reduce doping efficiency by sequestering ions.
- Removing side chains enhances ion access to the conjugated backbone, achieving doping efficiencies near unity.
- Materials with optimized doping efficiency showed increased volumetric charge density and improved charge transport.
- Resulting transistors exhibited high transconductance.
Conclusions:
- Effective volumetric capacitance is a superior metric for evaluating organic electrochemical transistors.
- Electronically effective doping, not solely ionic uptake, is critical for transistor performance.
- Side-chain engineering is a key strategy for designing high-performance organic mixed conductors.
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