Copper inclusion and migration from the back contact in CdTe solar cells

Metallic back contacts to CdS/CdTe solar cells will in general form Schottky barriers. Better performance is achieved with the inclusion of Cu in the back contact. This study uses current–voltage, capacitance–voltage, and laser beam induced current measurements to analyze as-deposited CdS/CdTe solar cells prepared with varying back-contact Cu amounts and to evaluate changes in cell performance following elevated-temperature stress. A simple model is proposed to explain both the observed differences in device behavior as copper is added or removed from the contact region, and how copper movement depends on electrical bias.