High-Performance Organic Electrochemical Transistors Based on PEDOT:PSS Doped with Reduced Manganese Dioxide

Fabricating a poly(3,4-ethylenedioxythiophene) (PEDOT):poly(4-styrenesulfonate) (PSS)-based organic electrochemical transistor (OECT) that simultaneously displays a high transconductance and a low threshold voltage remains challenging owing to the inherent trade-off between the charge carrier mobility and ionic accessibility. Here, we demonstrate that dissolving 1.2 mM MnO2 into 1 vol % ethylene glycol-treated PEDOT:PSS resolves this challenge via a Mn2+-mediated ionic scaffold mechanism: Mn2+ ions bridge adjacent PSS– chains, inducing ordered PEDOT lamellar stacking and benzoid-to-quinoid backbone planarization while increasing the bipolaron density via direct oxidative doping. Compared to those of the undoped PEDOT:PSS channel, the resulting PEDOT:PSS films exhibit 4.1-fold enhancements in conductivity (522.6 S cm–1) and 7.8-fold improvements in the products of their charge carrier mobilities and volumetric capacitances (102.7 F cm–1 V–1 s–1), with threshold voltages of only 0.33 V. Microchannel OECTs fabricated via photolithographic patterning display 2.2-fold improvements in transient switching speed (τ = 1.41 ms) and operational bandwidths of >200 Hz with levels of amplitude retention of 91%. They also exhibit robust cycling stabilities (96% over 1000 cycles) without the voltage penalties associated with their conventional highly conductive PEDOT:PSS counterparts. This study indicates that submillimolar MnO2 doping constitutes an effective, process-compatible strategy for use in decoupling the enhancement of the electrical conductivity from an increase in the threshold voltage of a PEDOT:PSS-based OECT. This provides a viable pathway toward high-speed, low-power bioelectronic sensing devices.