• Kodalle, T.; Schmidt, S.S.; Wolf, C.; Greiner, D.; Bloeck, U.; Schubert-Bischoff, P.; Kaufmann, C.A.; Schlatmann, R.: Investigating sulfur distribution and corresponding bandgap grading in Cu(In,Ga)(S,Se)2 absorber layers processed by fast atmospheric chalcogenization of metal precursors. Journal of Alloys and Compounds 703 (2017), p. 600-604

10.1016/j.jallcom.2017.01.329

Abstract:
A remarkable discrepancy between the optically active bandgap of Cu(In,Ga)(S,Se)2 absorber layers for thin film solar cells and the minimum bandgap as determined via elemental depth profiling has been observed in this study. This behavior occurs in absorbers sequentially grown by sulfurization after selenization of metal precursors and is demonstrated and explored in the following, using glow discharge optical emission spectroscopy, external quantum efficiency and Raman scattering. Furthermore this mismatch is explained by investigating the microscopic elemental distributions using transmission electron microscopy. It turns out, that sulfur is - on a microscopic scale - inhomogeneously distributed in the bulk of the absorber and solely present in areas near the absorber surface itself and at inner surfaces, e.g. in voids in the bulk.