1. IBM Research Europe─Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
2. Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
3. Laboratory for Thin Films and Photovoltaics, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
4. Université de Rennes, INSA Rennes, CNRS, Institut FOTON - UMR6082, 35000 Rennes, France