1. Debye Institute, Utrecht University, Princetonplein 1, 3584 CC Utrecht, The Netherlands
2. Optical Materials Engineering Laboratory, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland
3. Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands