Conjugated Radical Polymers for Organic Electrochemical Transistors

OECTs hold great potential in myriad applications, including neuromorphic devices, circuit elements, and bioelectronic sensors because OECTs are capable of transducing and amplifying ionic fluxes into the electronic signals with a high signal-to-noise ratio. The most oft-used electronically-active polymer implemented in OECTs is the commercially-available poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS); however, modifying the structure and electrochemical properties of PEDOT is difficult. Herein, we develop 3,4-propylenedioxythiophene (ProDOT)-based polymers which have much more readily tunable properties and chemical versatility relative to the EDOT-based polymers. In addition, we incorporate the nitroxide radical group (TEMPO) to the poly(3,4-propylenedioxythiophene) conjugated backbone to improve the electron and ion transport. The spectroelectrochemical analysis shows that as increasing positive potentials is applied, a polaron band appears at around 900 nm followed by the appearance of a bipolaron band as the potential increases to about 1.2 V. This work establishes the OECT performance of the P(ProDOT-TEMPO) polymer and determines the mixed ion-electron transfer mechanism for the conjugated radical polymer.