Nanodroplet-Embedded Semiconducting Polymer Layers for Electrochemically Stable and High-Conductance Organic Electrolyte-Gated Transistors

Organic electrolyte-gated transistors (OEGTs) utilizing high-capacitance ion gel dielectrics for low-voltage electronics often suffer from unintentional electrochemical doping processes (i.e., ion migration and charge transfer) and device degradation due to ion penetration into the semiconducting layer. Here, we report a simple and novel approach to fabricate a nanodroplet-embedded semiconducting polymer layer for reducing the undesired electrochemical doping processes of polymer-based OEGTs using poly(3-hexylthiophene) (P3HT) as a semiconducting layer and an insulating polymer/ionic liquid gel as a gate insulator. The semiconductor P3HT is cast from a stock solution blended with a small amount of ionic liquid (IL) as a nanodroplet component. Electrochemical devices employing the IL nanodroplet-embedded P3HT (P3HT/IL) film as an active layer exhibit ideal capacitive polarization and reliable transistor operation. Electrochemical impedance spectroscopy reveals that the P3HT/IL blends share a structural similarity with the gate dielectric ion gels. The IL nanodroplets dispersed in the active layer secure the local charge balance in the active layer and therefore reduce the slow electrochemical transport processes under applied biases. In OEGT characteristics, the current level of the nanodroplet-embedded devices becomes higher and more stable against operational bias stressing. Additionally, our devices show little hysteresis compared to that shown by the device of pristine P3HT without IL nanodroplets.