Radical Polymer-based Organic Electrochemical Transistors

The well-established design rules for organic electrochemical transistor (OECT) materials utilize various conjugated backbones with hydrophilic side chains to allow mixed electronic and ionic conduction to occur. To further our understanding of the underlying structure-property relations of OECT active layer materials, we design an OECT which incorporates a nonconjugated radical polymer in the active layer. Specifically, poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (PTEO) is blended with an oft-used conjugated polymer, poly(3-hexylthiophene) (P3HT), to create films with distinct closed-shell and open-shell domains. The well-defined oxidation-reduction (redox) potential associated with the radical moieties of the PTEO provides a sharp actuation feature that modulates the ionic transport and regulates doping of the P3HT phase within the blended film. Electrochemical analysis reveals that the blending strategy also improves packing within each domain. The present design strategy leads to figure-of-merit (i.e., µC*) values > 150 F V⁻¹ cm⁻¹ s⁻¹ at loadings as low as 5% PTEO (by weight), which is never-before-seen performance for a P3HT-based OECT. As such, this effort presents a design platform by which to readily create tailored OECT response through strategic macromolecular selection and polymer processing.