Damp heat related degradation mechanisms within CIGS solar cells

Degradation rates and mechanisms for molybdenum back contacts and ZnO:Al front contacts exposed to damp heat were obtained from literature and experiments. It was found that molybdenum back contacts with a higher density and covered by a MoSe₂ film are more stable than their low density, bare counterparts. For ZnO:Al front contacts, various material changes, including thickness, deposition temperatures and doping concentration increase as well as post-deposition treatments can lead to a more stable material. Moreover, the degradation rate of encapsulated and non-encapsulated CIGS solar cells and modules exposed to damp heat were determined It was observed that in general, exposure to damp heat led to a reduction in efficiency, mostly caused by a reduction in Voc and FF. However, it was found that very large differences exist between samples.