Rb Diffusion and Oxide Removal at the RbF-Treated GaO/Cu(In,Ga)Se Interface in Thin-Film Solar Cells.

We report on the chemical structure of Cu(In,Ga)Se (CIGSe) thin-film solar cell absorber surfaces and their interface with a sputter-deposited GaO buffer. The CIGSe samples were exposed to a RbF postdeposition treatment and an ammonia-based rinsing step, as used in corresponding thin-film solar cells. For a detailed chemical analysis of the impact of these treatments, we employed laboratory-based X-ray photoelectron spectroscopy, X-ray-excited Auger electron spectroscopy, and synchrotron-based hard X-ray photoelectron spectroscopy.