Polymeric mixed ionic–electronic conductors based on quinoid–azaisoindigo for n-type organic electrochemical transistors†

In the pursuit of channel materials for high-performance n-type organic electrochemical transistors (OECTs), several challenges have been encountered, including difficulties in the modification of the material structure, relatively low performance, and poor stability. To address these issues, designing innovative electron-deficient building blocks is critical for constructing novel donor–acceptor organic semiconductors with low LUMO levels to achieve high-performing n-type OECTs. In this study, we have designed and synthesized a novel glycolated quinone-based electron-deficient building block derived from azaisoindigo (AQM2I), featuring a cross-conjugated planar backbone and low LUMO levels, attributed to enhanced O–H interactions and strong electron-withdrawing amide groups. By combining AQM2I with alternating electron-rich building blocks (T, TT, 2T and 2FT), a series of novel n-type polymers that possessed mixed ionic–electronic conductivity were prepared. The incorporation of various electron-rich building blocks effectively modulates the backbone structure, molecular energy levels and sodium doping capability of the polymers. Moreover, a mixed conducting property with a maximum μC* figure-of-merit value of 0.53 F V⁻¹ cm⁻¹ s⁻¹ for accumulation-mode n-type OECT was achieved, attributed to the high electron mobility induced by the enhanced lamellar stacking, smooth and dense film morphology. The design strategy for novel electron-deficient building blocks presented in this work provides insights for the development of high-performance materials for n-type OECTs.