1. Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
2. Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455
3. Department of Electronics/Metrology, EMPA Material Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
4. Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland and Solar Technology Laboratory, Paul Scherrer Institute, 5232 Villigen, Switzerland