US Patent 7781673 Polymers with low band gaps and high charge mobility

This disclosure relates to a polymer containing a first comonomer repeat unit and a second comonomer repeat unit. The first comonomer repeat unit includes a cyclopentadithiophene moiety. The second comonomer repeat unit includes a thienothiophene moiety, a thienothiophene tetraoxide moiety, a dithienothiophene moiety, a dithienothiophene dioxide moiety, a dithienothiophene tetraoxide moiety, or a tetrahydroisoindole moiety. The polymer can be used as a photoactive material in a photovoltaic cell. This disclosure also relates to such photovoltaic cells, as well as modules containing such photovoltaic cells.