Molecular Doping of a High Mobility Diketopyrrolopyrrole–Dithienylthieno[3,2-b]thiophene Donor–Acceptor Copolymer with F6TCNNQ

Herein we present a molecular doping of a high mobility diketopyrrolopyrrole–dithienylthieno[3,2-b]thiophene donor–acceptor copolymer poly[3,6-(dithiophene-2-yl)-2,5-di(6-dodecyloctadecyl)pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophene], PDPP(6-DO)2TT, with the electron-deficient compound hexafluorotetracyanonaphthoquinodimethane (F6TCNNQ). Despite a slightly negative HOMOdonor–LUMOacceptor offset of −0.12 eV which may suggest a reduced driving force for the charge transfer (CT), a partial charge CT was experimentally observed in PDPP(6-DO)2TT:F6TCNNQ by absorption, vibrational, and electron paramagnetic resonance spectroscopies and predicted by density functional theory calculations. Despite the modest CT, PDPP(6-DO)2TT:F6TCNNQ films possess unexpectedly high conductivities up to 2 S/cm (comparable with the conductivities of the benchmark doped polymer system P3HT:F4TCNQ having a large positive offset). The observation of the high conductivity in doped PDPP(6-DO)2TT films can be explained by a...