Visible and x-ray spectroscopy studies of defects in CdTe

We have used electroluminescence (EL), photoluminesence (PL), and synchrotron x-ray fluorescence (XRF) to study some of the properties of defects related to Cu and Na in polycrystalline thin films of CdTe. Some samples were prepared by ion implantation of CdTe single crystals followed by thermal anneal to remove the damage. Others were prepared by magnetron sputtering on quartz or borosilicate glass followed by vapor CdCl₂ heat treatment. EL was studied from sputtered CdS/CdTe solar cell structures. We find that EL is very sensitive to defects induced by light soaking; ion implantation-induced damage can be annealed at 400 C to yield good PL; and synchrotron XRF shows the presence of substantial copper in films sputtered from nominally pure CdTe.