Microstructural characterization of Cu-poor Cu (In, Ga)Se2 surface layer

► Device-quality CIGS thin films are prepared by a three-stage evaporation process. ► The surface layer shows a gradually Cu-poor compositional distribution. ► The thickness of the surface layer is in the range of 50-100 nm. ► The surface and the bulk of the material exhibit similar crystal structure. ► The surface layer contains a large amount of dislocations.