Polymer solar cells with low-bandgap polymers blended with C70-derivative give photocurrent at 1 μm

Low-bandgap alternating polyfluorenes with different donor-acceptor-donor moieties were synthesized. Electrochem. and optical absorption measurement show that onset bandgaps of these polymers range from 1.2 to 1.5 eV. These polymers, blended with a C70-deriv. as acceptor, are used for solar cell fabrication. Devices show promising photovoltaic properties, and the spectral response of photocurrent covers all visible and near-IR wavelength regions with its onset extended to 1 mm. The best data gives a photocurrent d. of 3.4 mA/cm2, open circuit voltage of 0.58 V and power conversion efficiency of 0.7% under illumination of AM1.5 (1000 W/m2) from a solar simulator. [on SciFinder (R)]