Communication: The advantages of combining carbon nanotubes with conjugated polymers for high-efficiency photovoltaic devices are explored in this article. The preparation and optical properties of a composite of multiwalled carbon nanotubes (MWNTs) and poly(p-phenylene vinylene) (PPV) are reported and the efficiency of a photovoltaic device fabricated from the composite investigated. A quantum efficiency approximately twice that of the standard ITO device is reported. believed to be due in part to a complex interpenetrating network of polymer chains and MWNTs.