Ambipolar organic field-effect transistors based on diketopyrrolopyrrole derivatives containing different π-conjugating spacers

We report the synthesis and characterization of two new DPP-based small molecules, BTDPPCN and TTDPPCN. By variation of π-conjugating spacers from bithiophene to thieno[3,2-b]thiophene, a lower LUMO level is obtained for TTDPPCN, but both compounds have a similar band gap of about 1.6 eV. Under ambient conditions, the excellent ambipolarity of BTDPPCN is demonstrated by balanced charge carrier mobilities of 0.065 and 0.031 cm2 V−1 s−1 for n- and p-channels after thermal annealing. The FETs based on TTDPPCN films also showed ambipolar charge transport properties with a very high electron mobility of 0.80 cm2 V−1 s−1 upon thermal annealing at 90 °C and a hole mobility of 0.024 cm2 V−1 s−1 at 150 °C.