Photoluminescence study of Cu diffusion and electromigration in CdTe

Abstract
We report changes in the photoluminescence (PL) spectra associated with the diffusion of Cu in CdTe thin films used in CdTe/CdS solar cells. We studied films grown by vapor transport deposition and radio-frequency sputtering as well as single-crystal CdTe. The main effects of Cu diffusion appear to be the quenching of a donor-acceptor transition associated with Cd vacancies and the increase in intensity of a lower energy band due to deep acceptor states. The changes in junction PL are consistent with the movement of Cu+ ions in the electric fields near the CdS/CdTe junction.