Effects of thermal stressing on CdTe/CdS solar cells

The effects of thermal stressing on CdTe/CdS thin film solar cells have been investigated. Cadmium telluride solar cells fabricated by close-spaced sublimation, and contacted with Cu-based back contacts have been subjected to temperatures ranging from 70 to 120/spl deg/C in inert ambient for over 3500 hours. The average starting V/sub oc/ and ff for all stressed devices were 840 mV and 72% respectively. The devices were periodically removed from the stress environment and their light and dark J-V characteristics were measured. It has been found that all cells exhibited some degree of degradation, which was accelerated with temperature. Changes in device characteristics appeared to be gradual for temperatures in the range of 70-90/spl deg/C. In all cases a significant portion of the observed degradation took place within the first 500-600 hours. SIMS analysis indicated that the stress process resulted in Cu-accumulation near the CdTe/CdS junction, suggesting that Cu is at least partially responsible for the observed junction degradation.