Novel Benzo[1,2-b:4,5-b′]dithiophene-Benzothiadiazole Derivatives with Variable Side Chains for High-Performance Solar Cells

Low bandgap copolymers are prepared by incorporating thiophene-modified benzo[1,2-b:4,5-b'] dithiophene and alkyloxy or fluorine-modified benzothiadiazole as donor and acceptor units. These copolymers exhibit a high open-circuit voltage and short-circuit current density. Good power conversion efficiencies are demonstrated in solar cell studies, indicating their promising photovoltaic application as donor materials.