Side Chain Regioregularity Enables High-Performance and Sustainable Organic Electrochemical Transistors

High-performance organic electrochemical transistors (OECTs) with sustainable processes are crucial for bioelectronics and integration applications, but still face challenges in molecular design, as well as solvent-device compatibility. Herein, we introduced a unique synthetic protocol focused on regioselective chemistry for the development of a donor–acceptor polymeric mixed ionic–electronic conductor (PMIEC) with a well-defined side chain arrangement and demonstrated the superiority of side chain regioregularity in enhancing OECT performance. Furthermore, we pioneered the utilization of a green solvent, 2-methyl tetrahydrofuran (MeTHF), for depositing the active OECT channel layers. We found that the regioregular copolymer exhibited over three times higher μC* of up to 810 F cm⁻¹ V⁻¹ s⁻¹ compared to its regioirregular counterpart, thanks to improved crystallinity, reduced trap density of states (tDOS), and enhanced OECT hole mobility. Notably, this was achieved without the need for additional film post-treatments or specialized polymer fractionation techniques and stood among the highest values reported to date for green-solvent-processed OECTs. Our work represents a significant advancement in sustainable OECTs and highlights the importance of precise control over side chain regioregularity in developing high-performance PMIECs.