1. Royal Institute of Technology (KTH) Kistagången 16, 164 40 Kista, Sweden
2. National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
3. Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
4. Department of Electrical and Electronic Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan