Degradation in weathered crystalline-silicon PV modules apparently caused by UV radiation

Recently, we presented the results of a 5-year solar weathering study of commercial crystalline-Si modules that found a linear relationship between the observed slow (0.2%-0.5% per year) short-circuit current (I/sub sc/) degradation and the total UV exposure dose. Consideration of previous literature reports of I/sub sc/ degradation against our results indicated that encapsulation browning cannot be identified as the cause. This paper reviews these results and outlines a new testing program recently initiated at NREL. The program will attempt to verify if UV radiation is responsible for the degradation and determine if the degradation is related to the rapid initial light-induced metastability caused by oxygen contamination in boron-doped Si solar cells.