The degradation of multi-crystalline silicon solar cells after damp heat tests.

Lower performance of multi-crystalline silicon solar cells is usually observed after long-term damp heat test at 85 °C/85% relative humidity. Performance degradation is known to result from the loss in fill factor (FF) due to high series resistance. The causes of the increase in the series resistance are the reduction of the photovoltaic (PV) ribbon in the solder joint and the oxidation of surface on the front Ag finger by high thermal and moisture stress. Additionally, severe degradation by FF loss after damp heat originated from the contact resistance between Si and Ag fingers. Ag crystallites on Si wafer and bulk Ag at the edge of the Ag finger were partially oxidized and could not play a role in the current path of photo-generated electrons. [ABSTRACT FROM AUTHOR]