Light-induced metastability in hydrogenated nanocrystalline silicon solar cells

Light-induced metastability in hydrogenated nanocrystalline silicon (nc-Si:H) single-junction solar cells has been studied under different light spectra. The nc-Si:H studied contains a certain fraction of hydrogenated amorphous silicon $(a\text{-}\mathrm{Si}:\mathrm{H})$ . We observe no light-induced degradation when the photon energy used is lower than the bandgap of $a$ -Si:H, while degradation occurs when the photon energy is higher than the bandgap. We conclude that the light-induced defect generation occurs mainly in the amorphous phase. Light soaking experiments on $a\text{-}\mathrm{Si}:\mathrm{H}∕a\text{-}\mathrm{Si}\mathrm{Ge}:\mathrm{H}∕\mathrm{nc}\text{-}\mathrm{Si}:\mathrm{H}$ triple-junction solar cells show no light-induced degradation in the bottom cell, because the $a$ -Si:H top and a $a$ -SiGe:H middle cells absorb most of the high-energy photons.