Photoluminescence of CdTe:Cu and CdS:Cu [for solar cells]

The authors present results of Cu-related photoluminescence on CdTe and CdS single crystals doped by diffusion of thermally evaporated Cu. In CdTe:Cu their results are consistent with some Cu atoms occupying substitutional positions on the Cd sublattice and with others forming Frenkel pairs involving an interstitial Cu and a Cd vacancy. In addition, they find that Cu-related states in CdTe:Cu samples exhibit a significant reversible “aging” behavior. In CdS:Cu, the main effect of Cu diffusion is a quenching of the photoluminescence. They also show evidence of an exciton bound to a Cu-related site that is stable under short-term light illumination. In addition, a donor-acceptor pair transition may be observed in CdS:Cu using excitation energies below the transition emission energy. They show that the results are related to stability behavior of CdTe-CdS solar cells using Cu as a back contact