Patent ID: 7781673

Claim:
A photovoltaic cell, comprising: a first electrode, a second electrode, and a photoactive material disposed between the first and second electrodes, the photoactive material comprising a polymer including a first comonomer repeat unit and a second comonomer repeat unit, wherein the first comonomer repeat unit comprises a cyclopentadithiophene moiety, and the second comonomer repeat unit comprises a thienothiophene moiety of formula (XI): wherein each of R 5 and R 6 , independently, is H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 or SO 2 R, in which R is C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.