1. Experimental Condensed Matter Physics Laboratory, Department of Physics, University of Cyprus, Nicosia 1678, Cyprus
2. Department of Physics, Laboratory of Ultrafast Science, University of Cyprus, Nicosia 1678, Cyprus
3. Laboratory for Thin Films and Photovoltaics, Empa─Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf CH-8600, Switzerland
4. Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland