US Patent 7825330 Solar cell

A solar cell and photovoltaic power generation apparatus including a transparent electrically conductive film, a semiconductor provided on the transparent electrically conductive film, a conductive film opposing the semiconductor, and an electrolyte solution filled between the semiconductor and the conductive film. Metal ions, such as silver ions, may be dissolved in the electrolyte solution. When light is incident on the cell, the metal ions cause an oxidation-reduction reaction in the electrolyte solution and the cell is charged. When the open-circuit voltage decreases because the amount of incident light drops or light is blocked, the cell discharges to function as a secondary cell.