Terthiophene-cyanovinylene π-conjugated polymers as donor material for organic solar cells

Conjugated polymers of hybrid structure containing cyanovinylene linkages have been synthesized by Knoevenagel condensation of diformyl terthienyls with para-dicyanomethylbenzene. UV–vis and cyclic voltammetric data show that these polymers combine reduced band gap, improved light-harvesting properties and low lying HOMO level. Whereas the very low solubility of the polymers did not allow the fabrication of bulk heterojunction solar cells, bilayer heterojunction solar cells have been realized using thermally evaporated films of fullerene C60 as acceptor material. The best devices show a maximum external quantum efficiency of ∼20% and a power conversion efficiency of 0.40% under simulated AM 1.5 solar illumination.