We achieved the highest conversion efficiency of 9.5% in a large area amorphous silicon (a-Si) solar cell (40 cm×30 cm) for the first time in the world. It was achieved by employing surface technologies, such as, the optical confinement structure, the high quality a-Si fabrication technique, and high quality a-Si germanium technology. Using the a-Si technology HIT solar cell that is a hybrid of a-Si and c-Si was also developed. The conversion efficiency of a module using HIT solar cells is 15.2% that is the highest for the products. In addition to high conversion efficiency the HIT structure solar cell has an improved temperature dependence compared to conventional c-Si cells.