Light-induced degradation of thin film amorphous and microcrystalline silicon solar cells

Absorption spectra of two dilution series of microcrystalline solar cells deposited by VHF-PECVD were measured by FTPS. The dilution series were composed of pin and of nip cells, with i-layers ranging from highly crystalline to mainly amorphous. This paper evaluates stability of the cells when exposed to white light (AM 1.5-like spectrum). Defect-related absorption is minimum for cells of medium crystallinity (deposited in the transition region); but is increased for theses cells by a factor 2 to 4 under light-soaking. It still remains lower than that of highly crystalline cells which show very little degradation. Variation of electrical parameters is also investigated as a function of light soaking and annealing steps. Cells of medium crystallinity show approximately 10% reversible relative efficiency loss after 1000 hours of light soaking.