Electronic level alignment at the deeply buried absorber/Mo interface in chalcopyrite-based thin film solar cells

We have investigated the electronic structure of the absorber/back contact interface for S-free [Cu(In, Ga)Se(2) (CIGSe)] and S-containing [Cu(In, Ga)(S, Se)(2) (CIGSSe)] chalcopyrites with direct and inverse photoemission. Comparison of the electronic levels of the cleavage planes reveals a pronounced cliff in the conduction band at the CIG(S)Se/Mo interface. For the valence band, we find a flat alignment and a small spike for the CIGSe- and CIGSSe-based structures, respectively. (C) 2008 American Institute of Physics.