Impact of donor modification on azaisoindigo-based polymers for n- and p-type organic electrochemical transistors

Abstract

Polymeric organic mixed ionic-electronic conductors have shown remarkable potential as ideal semiconductor materials for organic electrochemical transistors (OECTs), which are emerging as a key technology in next-generation bioelectronics. While numerous conjugated donor–acceptor (D–A) materials based on thiophene, naphthalenediimide, and diketopyrrolopyrrole have been developed, isoindigo counterparts remain comparatively less explored. Herein, we report three D–A polymers based on azaisoindigo (AIG) as the acceptor unit, each containing different donor moieties: bithiophene (2T), difluorinated bithiophene (ff2T), and ethylenedioxy-substituted bithiophene (bisEDOT). By systematically varying the donor strength along the polymer backbone, we switch the dominant charge carrier from p-type with AIG-bisEDOT containing the most electron-rich donor moiety to n-type with AIG-ff2T incorporating the least electron-rich donor when tested in an OECT device configuration. The underlying structure–property relationships dictating this behaviour are elucidated by means of a joint experimental and computational approach.