Synthesis and photovoltaic characterization of thiadiazole based low bandgap polymers

Two copolymers comprised of different fused thiadiazole electron withdrawing units and benzo[1,2-b:4,5-b′]dithiophene electron donating unit have been synthesized by Stille reaction. The structural, optical, electrochemical and photovoltaic properties of the copolymers were investigated. Both copolymers in the film state exhibited abroad absorption spectra with an extremely low bandgap of ~ 1.2 eV. Bulk heterojunction solar cells were further fabricated and the best device delivered a power conversion efficiency of 0.52% when thermal annealed at 90 °C.