1. Fraunhofer Institute for Solar Energy Systems ISE; Heidenhofstr. 2 79110 Freiburg Germany
2. Freiburg Materials Research Center FMF; University of Freiburg; Stefan-Meier-Str. 21 79104 Freiburg Germany
3. Materials Science Department; Technische Universität Darmstadt; Jovanka-Bontschits-Str. 2 64287 Darmstadt Germany
4. InnovationLab GmbH; Speyerer Straße 4 69115 Heidelberg Germany
5. Institute of Physics; University of Freiburg; Hermann-Herder-Str. 3a 79104 Freiburg Germany
6. Institut de Sciences des Matériaux de Mulhouse; CNRS UMR 7361; 3bis rue Alfred Werner 68093 Mulhouse Cedex France