1. Fraunhofer Institute for Solar Energy Systems ISE, D-79110 Freiburg, Germany
2. Fraunhofer ISE , D-79110 Freiburg, Germany
3. Philipps University Marburg, D-35032 Marburg, Germany
4. Technische Universität Ilmenau, D-98693 Ilmenau, Germany
5. Institute of Materials Science , Christian-Albrechts-University, D-24118 Kiel, Germany