Hybrid Alkyl-Ethylene Glycol Side Chains Enhance Substrate Adhesion and Operational Stability in Accumulation Mode Organic Electrochemical Transistors

Donor-acceptor copolymers featuring electron-deficient isoindigo units and electron-rich 3,4-ethylenedioxy (EDOT) groups are presented as new materials for accumulation mode organic electrochemical transistors (OECTs). Grafting hybrid alkyl-ethylene glycol side chains on the isoindigo units of the copolymer leads to OECTs with outstanding substrate adhesion and operational stability in contact with an aqueous electrolyte, as demonstrated by their preserved performance after extensive ultrasonication (1.5 h) or after continuous on-off switching for over 6 h. Hybrid side chains outperform copolymers with alkyl only or ethylene glycol only side chains, which retain only 27% and 10% of the on currents after 40 min of on-off switching, respectively, under the same biasing conditions. These devices are promising candidates for in vitro and in vivo bioelectronics, applications where stability as well as robust adhesion of the conjugated polymer to the substrate are essential.