1. Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
2. Complex Compound Semiconductor Materials for Photovoltaics, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 14109 Berlin, Germany
3. University of Luxembourg, Laboratory for Photovoltaics, Physics and Materials Science Research Unit, L-4422 Belvaux, Luxembourg