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.
ACKNOWLEDGEMENT OF GOVERNMENT SUPPORT
 This invention was made with Government support under Contract Number DEFG02-91-ER45439 awarded by the U.S. Department of Energy (DOE). The Government has certain rights in the invention.