1. Institute for Semiconductor Technology, TU Braunschweig, Hans-Sommer-Strasse 66, Braunschweig 38106, Germany
2. Catalonia Institute for Energy Research, Jardins de les Dones de Negre 1, Barcelona 08930, Spain
3. Department d’Electrònica, Universitat de Barcelona, c/Martí Franquès 1, Barcelona 08028, Spain
4. TEM-MAT, CCiTUB, Solé i Sabarı́s 1, Barcelona 08028, Spain
5. Institute of Energy Research and Physical Technologies, TU Clausthal, Leibnizstrasse 4, Clausthal-Zellerfeld 38678, Germany
6. Institut de Ciència de Materials de Barcelona (ICMAB - CSIC), Campus UAB, Bellaterra 08193, Spain