Efficient photovoltaic cells from semiconducting polymer heterojunctions

Solar cells made from spin-coated bilayer thin-film heterojunctions of poly(p-phenylene vinylene) and poly(benzimidazobenzophenanthroline ladder) were found to have photovoltaic charge collection efficiency as high as 49%. The power conversion efficiency varied from 1.4% under sunlight illumination to 2.0% at the peak wavelength. A space-charge region around the polymer/polymer interface, Ohmic contacts at the electrodes, and complementary absorption bands of the semiconducting polymers, play important roles in the efficient charge collection in the photocells.