Low-bandgap conjugated polymers based on benzodipyrrolidone with reliable unipolar electron mobility exceeding 1 cm2 V−1 s−1

The employment of an intrinsic quinoidal building block, benzodipyrrolidone (BDP), on constructing conjugated polymers (PBDP-2F and PBDP-2CN) with high electron mobility and unipolar transport characteristic in polyethylenimine ethoxylated (PEIE) modified organic field-effect transistors (OFETs) is reported. The intrinsic quinoidal characteristic and excellent co-planarity of BDP can lower the lowest unoccupied molecular orbital (LUMO) levels and improve ordered interchain packing of the resulting polymers in solid states, which are favorable for electron-injection and transport. By using PEIE as the interlayer to block the hole injection, unipolar n-type transport characteristics with high electron mobility of 0.58 and 1.01 cm2 V−1 s−1 were achieved by the OFETs based on PBDP-2F and PBDP-2CN, respectively. More importantly, the extracted mobilities are highly reliable with the reliability factor of above 80%. To the best of our knowledge, PBDP-2CN is the very first quinoid-based conjugated polymer with reliable electron mobility exceeding 1 cm2 V−1 s−1. This work represents a significant step in exploring intrinsic quinoidal CPs for application in n channel OFETs and logic complementary circuits.