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%. Th e power conversion efficiency varied from 1.4% under sunlight illumination to 2.0% at the peak wavelength. A space-charge region around the polymer/po lymer interface, Ohmic contacts at the electrodes, and complementary absorp tion bands of the semiconducting polymers, play important roles in the effi cient charge collection in the photocells. (C) 2000 American Institute of P hysics. [S0003-6951(00)02943-0].