Novel structures of photovoltaic cells (also treated as solar cells) are provided. The cells are based on nanometer or micrometer-scaled wires, tubes, and/or rods, which are made of electronic materials covering semiconductors, insulators, and may be metallic in structure. These photovoltaic cells have large power generation capability per unit physical area over the conventional cells. These cells will have enormous applications such as in space, commercial, residential and industrial applications.