Direct determination of the band alignment at the (Zn,Mg)O/CISSe interface

The electronic and chemical properties of the $(Zn1−x,Mgx)O/CuIn(S,Se)2$ interface, prepared by sputtering of thin (Zn,Mg)O layers, were investigated with direct and inverse photoelectron spectroscopy on in situ prepared samples. With the combination of both techniques we have determined the band alignment at this interface as a function of Mg-content in the range $0≤x≤0.30$⁠. We find that the band alignment at the interface can be tailored between a “cliff” (downward step) in the conduction band for pure ZnO and a “spike” (upward step) for high Mg-contents. A direct influence of the band alignment modifications on the solar cell parameters is found.