Narrow Bandgap-Conjugated Polymers Incorporating Thieno[3,2‑c]pyridine-4,6-Dione-Derived Isoindigo for Organic Field-Effect Transistor Applications

A building block of thieno[3,2-c]pyridine-4,6-dione-derived isoindigo (TPyI) was designed and synthesized. TPyI has a planar structure with strong S···O noncovalent interactions according to both quantum chemistry simulations and single-crystal structure information. Two TPyI-based D–A polymers, including regioirregular and regioregular versions (ri-PTPyI2T and rr-PTPyI2T), were synthesized since TPyI is geometrically asymmetrical. The polymer thin films exhibited narrow bandgaps of approximately 1.19 eV and p-type charge transport characteristics, with maximum hole mobilities of 0.14 cm²/(V s) for ri-PTPyI2T and 0.32 cm²/(V s) for rr-PTPyI2T, respectively. This study highlights the design and synthesis of TPyI-based narrow band gap-conjugated polymers that are promising for organic electronics.