High efficiency graphene/wide band-gap semiconductor heterojunction solar cells

A photovoltaic solar cell apparatus comprising:

• a foil substrate consisting essentially of zinc;
• a plurality of nanowire cores on the foil substrate, the nanowire cores comprising zinc oxide, wherein at least a majority of the nanowire cores are substantially aligned to one another and extend generally perpendicular to the foil substrate and electrically connected to the foil substrate at a first end of the nanowire cores;
• a substantially continuous coating of zinc oxide on the foil substrate between the nanowire cores;
• a plurality of shells, each comprising graphene, and each shell being conformally disposed about a portion of a respective nanowire core to form a plurality of nanowire core/shell structures;
• a first conducting electrode electrically connected to the foil substrate and providing a first electrical pathway to facilitate a movement of electrons away from the nanowire cores;
• a second conducting electrode connected to shells at a second end of the nanowire core/shell structures and providing a second electrical pathway to facilitate a movement of positive charges away from the shells;
• and
• the second conducting electrode comprising a material that is at least partially transparent to sunlight and at least one metal effective to reduce the work function of the shells within at least a portion of the partially transparent material.