PBDB-T Accessed via Direct C–H Arylation Polymerization for Organic Photovoltaic Application

Poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′] dithio-phene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))] (PBDB-T), one of the most important donor polymers in organic photovoltaics (OPVs), is successfully synthesized, for the first time, via atom-economic direct C–H arylation polymerization (DArP). We systematically investigated the effects of reaction parameters on the molecular weights, polydispersity index, optical properties, device performance, and morphologies. Five batches of PBDB-T (P1–P5) with different molecular weights are synthesized under varied DArP conditions. Among them, P5 synthesized with the assistance of tetramethyl-ethylenediamine (TMEDA) co-ligand shows the best performance for OPV device, yielding a 6.52% power conversion efficiency (PCE) in the bulk heterojunction pairing with ITIC. Briefly, an optimal DArP protocol toward PBDB-T has been developed in the current study, which will provide a guideline for the synthesis of high-performance OPV materials in an atom-economic way.