Design, Synthesis and Properties of Low Band Gap Polyfluorenes for Photovoltaic Devices

Two new alternating polyfluorene copolymers containing different low band gap segments have been designed and synthesized for use in optoelectronic devices. The low band gap segments consist of electron donating and accepting moieties which induce a partial charge transfer in the polymer backbone and thereby, a lower band gap. Results obtained from characterization of the new materials, called APFO-Green1 and APFO-Green2, include absorption and emission at extended wavelengths as well as high stability. Furthermore, blends of the new copolymers with different fullerene derivatives exhibit unprecedented photovoltaic behavior at long wavelengths.