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Comprehensive Summary: Diketopyrrolopyrrole (DPP) is one of the most promising building blocks for constructing polymer semiconductors with high charge‐carrier mobilities in organic field‐effect transistors (OFETs). In this study, a novel DPP‐based conjugated polymer, PDPPy‐BDD, was designed and synthesized. The ambipolar field‐effect transistor characteristics were realized with the average hole and electron mobilities of 3.5 × 10–3 and 3.07 × 10–2 cm2 V−1 s−1, respectively. Both the hole and electron mobilities could be successfully enhanced by using a tetramethylammonium iodide (NMe4I) additive. Such an enhancement was attributed to the formation of stronger interchain π–π stackings, the weakening of the face‐on packing orientation in the thin film state, and the higher channel conductivities in the OFETs. [ABSTRACT FROM AUTHOR]

Methoxy-substituted thiophene units were incorporated into a diketopyrrolopyrrole and quaterthiophene based copolymer to produce random copolymers. Inclusion of the methoxy group narrowed the optical energy gap of the resulting copolymers owing to the enhanced planar backbone that results in more effective conjugation. At a low loading ratio of 25mol% random copolymer exhibited a hole mobility of ~0.3 cm2 V−1 s−1 comparable to that of the diketopyrrolopyrrole and quaterthiophene based original polymer. Although increasing the methoxy-substituted thiophene ratio in the polymers resulted in decreased molecular weights, it was concluded that incorporation of the methoxy-substituted thiophenes enhanced the hole mobility from 0.02 cm2 V−1 s−1 for 50mol% loading to 0.07 cm2 V−1 s−1 for 100mol% loading. The enhancement was attributed to the formation of pre-aggregates with stronger interchain interactions with increasing backbone coplanarity, resulting in edge-on dominant and bimodal edge-on/face-on molecular packing orientations. The addition of tetramethylammonium iodide as an ionic additive proved not to be an effective method for improving the performance of polymers containing the methoxy-substituted thiophenes, whereas the original polymer displayed a noticeable improvement of the charge transport properties. Image 1 • The new planar structural unit of 3,3′-dimethoxybithiophene was incorporated into DPP-based semiconducting polymers. • The introduced 3,3′-dimethoxybithiophene unit lowered the optical band gap due to the enhanced planar backbone. • The introduced 3,3′-dimethoxybithiophene unit enhanced the charge transport properties due to the bimodal packings. • The addition of Me 4 NI improved the charge transport properties when the 3,3′-dimethoxybithiophene unit was absent. [ABSTRACT FROM AUTHOR]