Study of metastability in hydrogenated nanocrystalline silicon solar cells

Light-induced metastability in hydrogenated nanocrystalline silicon (nc-Si:H) single-junction solar cells has been studied systematically under various conditions. We observe no light induced degradation when the photon energy used is smaller than the bandgap of hydrogenated amorphous silicon (a-Si:H); while degradation occurs when the photon energy is larger than the bandgap. We conclude that the light-induced defect generation occurs mainly in the amorphous phase. Contrary to a-Si:H cells, a forward current injection does not degrade the c-Si:H cell performance. However, applying a reverse bias during light soaking unexpectedly enhances the light-induced degradation.