1. Center for Nanophotonics, AMOLF, Science Park 104, Amsterdam 1098 XG, The Netherlands
2. Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, United-Kingdom
3. Laboratory for Thin Films and Photovoltaics, EMPA − Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, Dübendorf 8600, Switzerland
4. Debye Institute for Nanomaterials Science, Utrecht University, Princetonlaan 6, Utrecht 3584 CB, The Netherlands