“Two-in-One” DPP Building Blocks for Ambipolar Conjugated Polymers in Flexible Transistors
Bolun Huang, Pinyu Chen, Xinqiang Hua, Dongsheng Qiu, Tianqiang Cui, Jiulong Zhang, Shuxian Zhang, Chengshan Yuan, Feng He, Xiangfeng Shao, Hao‐Li Zhang, Zitong Liu
Abstract
Advancements in conjugated donor–acceptor (D–A) polymers with superior semiconducting performance and reliability are pivotal to the evolution of flexible electronics. However, the development of electron-accepting building blocks has lagged far behind that of electron-donating ones, hindering the progression of ambipolar and n-type semiconductor polymers―especially ambipolar types―and thereby limiting the construction of logic circuits and p–n heterojunctions. In this study, we introduce a new electron-accepting building block, 2Ar’Ar2DPP, meticulously engineered for semiconducting polymers tailored to flexible electronics applications. Synthesized through the modification of conventional diketopyrrolopyrrole (DPP), 2Ar’Ar2DPP ─including 2TPh2DPP and 3T2DPP ─incorporates structural innovations, merging a single DPP unit with two aromatic groups into a configuration featuring two DPP units and three aromatic groups. This modification enhances the electron-accepting ability and modulates intra- and intermolecular D–A interactions. 2TPh2DPP and 3T2DPP were investigated to explore their structure–property relationships. Specifically, 3T2DPP demonstrates improved backbone planarity, extended π-conjugation, and more efficient intramolecular D–A interactions. These features result in significantly lower LUMO levels and narrower band gaps compared to those of conventionally utilized thiophene-flanked DPP and even its dimer. Moreover, the change in the molecular structural symmetry of 3T2DPP induces a relatively large dipole moment, thereby enhancing intermolecular interactions. Consequently, polymers derived from 2Ar’Ar2DPP exhibit ambipolar semiconducting performance in flexible organic field-effect transistors, achieving hole and electron mobilities of up to 6.0 and 2.1 cm 2 V –1 s –1, respectively, with good bending resistance. These preliminary results indicate that 2Ar’Ar2DPP holds significant promise for the future design of conjugated materials for flexible electronics.