techniques for combining nanotechnology with photovoltaics are provided . in one aspect , a method of forming a photovoltaic device is provided comprising the following steps . a plurality of nanowires are formed on a substrate , wherein the plurality of nanowires attached to the substrate comprises a nanowire forest . in the presence of a first doping agent and a first volatile precursor , a first doped semiconductor layer is conformally deposited over the nanowire forest . in the presence of a second doping agent and a second volatile precursor , a second doped semiconductor layer is conformally deposited over the first doped layer . the first doping agent comprises one of an n - type doping agent and a p - type doping agent and the second doping agent comprises a different one of the n - type doping agent and the p - type doping agent from the first doping agent . a transparent electrode layer is deposited over the second doped semiconductor layer .