Substrate versus superstrate configuration for stable thin film silicon solar cells

We report on the light-induced degradation kinetics of hydrogenated polymorphous silicon (pm-Si:H) solar cells having either substrate or superstrate device configuration. Both types of devices were exposed to light-soaking for 500 h. While pm-Si:H superstrate solar cells showed strong degradation (up to 60%) under mercury vapor lamp illumination, we have found that substrate structures are remarkably stable. The difference between the two types of devices is shown to be related to interface delamination which only occurs in superstrate devices. We further demonstrate a strong correlation between short-circuit current density decrease upon light-soaking and solar cell area loss.