Backbone Engineering of Bithiophene Imide Dimer‐Based Polymeric Mixed Ionic‐Electronic Conductors for High‐Performance n‐Type Organic Electrochemical Transistors

Abstract Polymeric mixed ionic‐electronic conductors (PMIECs) are gaining significant attention due to their potential applications in organic electrochemical transistors (OECTs). However, the performance of n‐type OECTs still lags behind that of their p‐type counterparts. Here, the structure‐performance correlation of fused bithiophene imide dimer (BTI2)‐based PMIECs is systematically investigated with the backbone evaluation from acceptor‐strong donor (A‐SD) to acceptor‐donor (A‐D), to acceptor‐weak donor (A‐WD), to acceptor‐weak acceptor (A‐WA), and finally to A‐A structures. Compared to other PMIECs, the A‐A backbone‐based PMIEC PBTI2g‐BTI features the most suppressed lowest unoccupied molecular orbital energy level, a highly planar backbone, and superior n‐type electrochemical dopability. Consequently, polymer PBTI2g‐BTI delivers an exceptional unipolar n‐type OECT performance with a high electron mobility of 0.25 cm 2 V⁻¹ s⁻¹ and a remarkable µC * value of 63.79 F cm⁻¹ V⁻¹ s⁻¹, both of which are significantly higher than those of other types of PMIECs. This study demonstrates that the A‐A backbone strategy is an effective approach to developing high‐performance n‐type PMIECs for applications in OECTs.