Photovoltaics (electric power generation directly from sunlight using solar cells) have attracted worldwide attention as a new energy source because of its cleanness and potential contributing to energy supply. For widespread introduction of photovoltaic power generation, further improvements in the conversion efficiency and reducing the cost of the solar cells are necessary. This paper reviews potential and technical problems of silicon solar cells as one of the most promising next generation solar cells. As next generation solar cells, silicon thin films (amorphous, microcrystalline and poly-crystalline) and solar cells should be researched and developed actively for widespread applications of photovoltaics.