Naphthobisthiadiazole-Based Selenophene-Incorporated Quarterchalcogenophene Copolymers for Field-Effect Transistors and Polymer Solar Cells

In this research, we developed six new selenophene-incorporated naphthobisthiadiazole-based D-A polymers PNT2Th2Se-OD, PNT2Se2Th-OD, PNT4Se-OD, PNT2Th2Se-DT, PNT2Se2Th-DT and PNT4Se-DT. The structure-property relationships have been systematically established through the comparison of their structural variations: (1) isomeric biselenophene/bithiophene arrangement between PNT2Th2Se and PNT2Se2Th polymers, (2) biselenophene/bithiophene and quarterselenophene donor units between PNT2Th2Se/PNT2Se2Th and PNT4Se polymers, (3) side-chain modification between the OD- and DT-series polymers. The incorporation of selenophene unit in the copolymers induces stronger charge transfer to improve the light-harvesting capability while maintaining the strong intermolecular interactions to preserve the intrinsic crystallinity for high carrier mobility. The OFET device using PNT2Th2Se-OD achieved a high hole-mobility of 0.89 cm2 V-1 s-1 with an on/off ratio of 2.4×106. The solar cells with PNT2Th2Se-OD:PC71BM exhibited a pow...