Raman spectroscopy of PIN hydrogenated amorphous silicon solar cells

Light-induced degradation of hydrogenated amorphous silicon (a-Si:H) is a key issue for enhancing competitiveness in solar cell market. A-Si:H films with a lower density of Si-H$_{2}$ bonds shows higher stability [1]. Here we identified Si-H$_{2}$ bonds in PIN a-Si:H solar cells fabricated by plasma CVD using Raman spectroscopy. A-Si:H solar cell has a structure of B-doped $\mu $c-SiC:H (12.5 nm)/ non-doped a-Si:H (250nm)/ P-doped $\mu $c-Si:H (40 nm) on glass substrates (Asahi-VU). By irradiating HeNe laser light from N-layer, peaks correspond to Si-H$_{2}$ bonds (2100 cm$^{-1})$ and Si-H bonds (2000 cm$^{-1})$ have been identified in Raman scattering spectra. The intensity ratio of Si-H$_{2}$ and Si-H I$_{\mathrm{SiH2}}$/I$_{\mathrm{SiH}}$ is found to correlate well to light induced degradation of the cells Therefore, Raman spectroscopy is a promising method for studying origin of light-induced degradation of PIN solar cells.\\[4pt] [1] T. Nishimoto, et al., J. Non-Crystal. Solids 299-302 (2002) 1116.