Optoelectronic Properties of a Benzodithiophene-Based Organic Photovoltaic

Benzo[1,2-b:4,5-b′]dithiophene (BDT) contains electron donating groups and conjugates with acceptor material as a donor-acceptor type conjugated polymer, which can be applied in bulk heterojunction organic photovoltaics due to its high charge carrier mobility. In this study, we used Stille coupling polymerization to synthesize a BDT monomer with thiophene side-chains and copolymerized with dioctyl 2,5-dibromoterephthalate (DTP) to form a 2-D type donor-acceptor conjugated polymer, BDT-DTP. Thermal analyses indicated that BDT-DTP has a high thermal decomposition temperature of 342.07 °C (weight loss = 5%), showing excellent thermal stability. The active layer comprised of BDT-DTP:3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))−5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC) blended film in a OPV device could achieve a power conversion efficiency of 1.08%, open-circuit voltage of 0.88 V, short-circuit current density of 4.08 mA cm⁻², and fill factor of 30.1%. This work demonstrates a novel structure of benzodithiophene-based donor material used in the photovoltaic application.