1. IEK-5 Photovoltaik, Forschungszentrum Jülich, 52425 Jülich, Germany
2. Institute of Advanced Materials, Universitat Jaume I, Castellón de la Plana 12071, Spain
3. Faculty of Engineering and CENIDE, University of Duisburg-Essen, Carl-Benz-Str. 199, 47057 Duisburg, Germany