Well-defined alternative polymer semiconductor using large size regioregular building blocks as monomers: electrical and electrochemical properties

Regioregular polymer semiconductors have demonstrated a well-ordered micro-crystalline morphology in thin films due to better π-stacking orientation resulting in efficient charge transport. We propose an effective synthetic strategy to achieve well-defined regioregular alternative donor–acceptor (D–A) type conjugated polymers using large molecular weight regioregular monomers. Using this synthetic route, various conjugated moieties can be systematically introduced in a single polymer backbone, and we developed a regioregular alternative D–A polymer, coded rr-PBTTh, based on thiophene as electron donating and benzothiadiazole as electron withdrawing groups. This new polymer possesses a highly planar conjugated backbone due to regioregularity and S⋯O and S⋯F non-covalent intramolecular conformational locks. rr-PBTTh exhibits well-balanced ambipolar transport characteristics mainly due to the balanced D–A molecular structure, and shows promising electrochromic performance with coloration efficiency up to 321.7 cm² C⁻¹ and rapid response time below 0.5 s.