Ambipolar Semiconducting Polymers with π-Spacer Linked Bis-Benzothiadiazole Blocks as Strong Accepting Units

Recognizing the importance of molecular coplanarity and with the aim of developing new, ideal strong acceptor-building units in semiconducting polymers for high-performance organic electronics, herein we present a simplified single-step synthesis of novel vinylene- and acetylene-linked bis-benzothiadiazole (VBBT and ABBT) monomers with enlarged planarity relative to a conventionally used acceptor, benzothiadiazole (BT). Along these lines, four polymers (PDPP-VBBT, PDPP-ABBT, PIID-VBBT, and PIID-ABBT) incorporating either VBBT or ABBT moieties are synthesized by copolymerizing with centro-symmetric ketopyrrole cores, such as diketopyrrolopyrrole (DPP) and isoindigo (IID), and their electronic, physical, and transistor properties are studied. These polymers show relatively balanced ambipolar transport, and PDPP-VBBT yields hole and electron mobilities as high as 0.32 and 0.13 cm2 V–1 s–1, respectively. Interestingly, the acetylenic linkages lead to enhanced electron transportation in ketopyrrole-based polymers, showing a decreased threshold voltage and inverting voltage in the transistor and inverter devices, respectively. The IID-based BBT polymers exhibit the inversion of the dominant polarity depending on the type of unsaturated carbon bridge. Owing to their strong electron-accepting ability and their highly π-extended and planar structures, VBBT and ABBT monomers should be extended to the rational design of high-performance polymers in the field of organic electronics.