Over 15% Efficient Hydrogenated Amorphous Silicon Based Triple-Junction Solar Cells Incorporating Nanocrystalline Silicon

We report our recent progress in the optimization of a-Si:H, a-SiGe:H, and nc-Si:H materials for high efficiency triple-junction solar cells. The main technique for the optimization of a-Si:H and a-SiGe:H materials is using hydrogen dilution to approach the amorphous to nanocrystalline transition. The nc-Si:H intrinsic layers are deposited using a modified VHF glow discharge technique at high rates. The material quality and cell performance are improved by using hydrogen dilution profiling for controlling the nanocrystalline evolution. Two triple-junction structures have been studied. We achieve an initial active-area efficiency of 15.1% using an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure, and 14.1% using an a-Si:H/nc-Si:H/nc-Si:H configuration. After prolonged light soaking, both structures stabilized at 13.3%, which is higher than the 13.0% stable efficiency previously reported for an a-Si:H/a-SiGe:H/a-SiGe:H triple-junction structure