1. University of Barcelona; Department of Electronics, Faculty of Physics; C. Martí i Franquès 1 08028 Barcelona Spain
2. IREC - Catalonia Institute for Energy Research; C Jardins de les Dones de Negre 1 08930 Sant Adria del Besos Barcelona Spain
3. Martin-Luther-University Halle-Wittenberg; Photovoltaics Group/Institute of Physics; Von-Danckelmann-Platz 3 06120 Halle (Saale) Germany
4. Federal Institute for Materials Research and Testing; Richard-Willstätter-Str. 11 12489 Berlin Germany