1. Renewable and Sustainable Energy Institute (RASEI), University of Colorado, Boulder, Boulder, Colorado 80303, United States
2. Materials Science and Engineering Program, University of Colorado, Boulder, Boulder, Colorado 80303, United States
3. Department of Chemistry−Ångström Laboratories, Uppsala University, Box 523, SE75120 Uppsala, Sweden
4. Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
5. IOM CNR Laboratorio TASC, 34149 Basovizza (TS), Italy
6. Department of Physics, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
7. Department of Chemistry, University of Colorado, Boulder, Boulder, Colorado 80303, United States