Efficient vacuum-deposited organic solar cells based on a new low-bandgap oligothiophene and fullerene C60

Organic solar cells based on a new oligothiophene derivative (see figure) and fullerence C-60 exhibit power efficiencies of up to 3.4%. alpha,alpha'-Bis(2,2-dicyanovinyl)-quinquethiophene (DCV5T) features a reduced optical gap with high absorption coefficients between 450 and 650 nm. Dicyanovinyl substituents on the oligothiophene rings lower the bandgap and increase the ionization energy of these oligomers, enabling the formation of photoactive heterojunctions with C-60 and yielding open-circuit photovoltages as high as 1 V.