Surface roughness, optical and spectroscopic properties of thin film systems based on Cu(In,Ga)Se2 absorbers

We study the behaviour of the local properties like surface roughness, splitting of the quasi Fermi levels and optical threshold energies of thin film systems based on Cu(In,Ga)Se2 absorbers and consisting of substrate, back electrode, Cu(In,Ga)Se2 absorbers, buffer layer and front electrode. We imitate in-situ experiments with lateral resolution such as afm-topology, spectral transmission/absorption and spectral photoluminescence, which announces the splitting of the quasi-Fermi levels by statistical methods for feature extraction like 2D Fourier transforms and/or Minkowski-operations (opening functions) by analyzing films from different states of the growth process, say of different thicknesses. We moreover correlate the above mentioned lateral features for the identification of the origin of final grainy structures as well as for that of lateral inhomogeneities.