Identification of defect levels in CdTe/CdS solar cells using deep level transient spectroscopy

Defect levels in CdTe/CdS have been characterized using correlation deep level transient spectroscopy. The devices studied were processed under various conditions in an effort to identify defect levels and correlate their presence to key processes and impurities. Process variations included the CdCl₂ treatment, as this process is very common to most CdTe technologies, and the back contact. The back contact often relies on the use of copper, an impurity known to be critical for the formation of effective back contacts, but which has also been associated with device degradation in CdTe solar cells. Several hole and electron traps were identified and are presented in this paper.