Dithiene-fused quinoxalineimide-based all-acceptor polymers for n-type organic semiconductors

Introduction of strong electron-deficient building blocks into the polymer backbone is an efficient strategy to design n-type organic semiconductors. In this work, a strong electron-deficient building block, dithiene-fused quinoxalineimide (DTQI), containing electron-withdrawing quinoxaline and imide units, was synthesized and incorporated into a polymer backbone. The frontier molecular orbital (FMO) energy levels downshifted with the incorporation of the quinoxalineimide (QI) unit onto the framework. Owing to the high electron-affinity of DTQI, the DTQI-based acceptor-acceptor (all-acceptor, A-A) type polymer P(DTQI-BTI) showed deep-lying highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, thus yielding unipolar n-type transport character with electron mobility of 0.25 cm(2) V-1 s(-1) in organic thin-film transistors. These results demonstrate that DTQI is a promising building block for constructing n-type polymer semiconductors and can be extended to the design of other novel electron-deficient building blocks.