Analysis of stress-induced degradation in CdS/CdTe solar cells

Accelerated stressing of CdS/CdTe solar cells at elevated temperatures (60-100 degreesC) under a range of applied bias in light and dark has identified three degradation modes: formation of a blocking contact, increased junction recombination, and increased dark resistivity. Devices with Cu-contacts degrade with a strong bias dependence. The blocking contact is formed under forward bias. Junction degradation requires both higher temperature and forward bias. Recontacting the device after stress removes the blocking contact with no change in junction losses. Devices without Cu in the contact have much poorer initial performance but degrade nearly independent of bias.