1. Department of Materials & Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel
2. Institute of Solid State Physics, Graz University of Technology, A-8010 Graz, Austria
3. National Renewable Energy Laboratory, Golden, Colorado 80401, United States
4. Department of Chemical Research
Support, Weizmann Institute of Science,
Rehovoth 76100, Israel