12.0% Efficiency on Large-Area, Encapsulated, Multijunction nc-Si:H-Based Solar Cells

Because of its superior long-wavelength response and stability against light-induced degradation, hydrogenated nanocrystalline silicon (nc-Si:H) has become a promising candidate to replace hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) in multijunction thin-film silicon solar cells. In this paper, we report on the development of our proprietary high-frequency (HF) glow discharge deposition technology for nc-Si:H solar cells that has resulted in high-quality nc-Si:H materials with good spatial uniformity. We studied the HF-deposited nc-Si:H material using various analytical techniques. We fabricated a-Si:H/nc-Si:H/nc-Si:H triple-junction solar cells that are deposited on textured Ag/ZnO back reflectors. Large-area cells were fabricated and encapsulated using our proprietary lightweight flexible encapsulants. National Renewable Energy Laboratory (NREL) has confirmed (1) initial aperture-area efficiency of 11.8% on an 807.8-cm² encapsulated cell and (2) stable aperture-area efficiency of 11.2% on a 400-cm² encapsulated cell.