1. Zernike Institute for Advanced MaterialsUniversity of Groningen Nijenborgh 4 Groningen 9747 AG The Netherlands
2. Department of Chemistry and Applied BiosciencesLaboratory of Inorganic ChemistryETH Zürich Vladimir-Prelog-Weg 1 Zürich CH-8093 Switzerland
3. Laboratory for Thin Films and PhotovoltaicsEmpa − Swiss Federal Laboratories for Materials Science and Technology Überlandstrasse 129 Dübendorf CH-8600 Switzerland