Donor–acceptor (D-A) and donor–donor (D-D) type thienothiophene based copolymers bearing benzothiadiazole, benzotriazole and dihexyloxybenzene units

Conjugated polymers have emerged as versatile semiconducting materials with tunable optical and electronic properties, making them highly attractive for organic electronic devices such as organic photovoltaics (OPVs), organic field-effect transistors (OFETs), and light-emitting devices. In this study, three nonyl-substituted thieno[3,2-b]thiophene based polymers were designed and synthesized; two donor–acceptor (D–A) type polymers incorporating the acceptors benzothiadiazole (BTD) and benzotriazole (BTZ) with the donor TT (TT–BTD and TT–BTZ), and one donor–donor (D–D) type polymer incorporating 1,4-dihexyloxybenzene and TT (TT–DHB). Considering D-A and D-D type molecular skeletons, the polymers showed remarkable and adjustable photophysical properties. Their optical/electronic band gaps were between 2.21 and 2.93 eV with a long-range absorption ranging from 225 to 600 nm. These findings demonstrated that the electronic and optical properties of TT-C9-based polymers can be precisely tuned through rational molecular design, emphasizing the potential of TT-BTD as a high-performance candidate for OPVs, OFETs, and other optoelectronic applications. This work provides valuable insights into the role of acceptor strength in tailoring polymer properties and highlights the design strategy for next-generation organic semiconductors.