Low-cost triple junction solar cells, which much attention has been paid to by industry, are studied in this paper. Based on the amorphous silicon/amorphous silicon tandem solar cells realized in industry using completely single chamber deposition technique, amorphous silicon/amorphous silicon/microcrystalline silicon triple junction solar cell with 9.52% conversion efficiency is fabricated by changing deposition conditions for microcrystalline bottom solar cell and n-p junction in a single chamber developed on our own.