Abstract: Photovoltaic cells and methods for making photovoltaic cells are provided. The photovoltaic cells include a photoactive layer which includes an array of elongated vertically aligned nanostructures. The nanostructures include at least a first and a second semiconducting material. The photovoltaic layer may also include a transparent insulating material which serves a passivation function.

Abstract: The invention provides methods for growing an array of elongated nanostructures projecting from a surface. The nanostructures of the array are aligned substantially perpendicularly to the surface. In one aspect of the invention, the diameter of the nanostructures is between 10 nm and 200 nm. The methods of the invention can produce nanostructure growth at temperatures less than 350 degrees Celsius. Alignment of the nanostructures does not rely on epitaxial growth from a single crystal substrate, allowing a variety of substrates to be used.