Cathodoluminescence of Cu diffusion in CdTe thin films for CdTe/CdS solar cells

We investigate the distribution of Cu acceptor states in CdTe thin films used in high-efficiency solar cells. These states are CuCd and Cui+–VCd− complexes, which are relatively deep and shallow acceptors, respectively. Cathodoluminescence spectroscopy and imaging show that, first, CuCd and Cui+–VCd− do not coexist and, second, the primary diffuser is represented by Cui+–VCd− complexes. Our results are used to discuss the effect of grain boundaries on Cu diffusion.