1. National Renewable Energy Laboratory, Golden, Colorado 80401, United States
2. Swift Solar Inc., San Carlos, California 94070-5321, United States
3. SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
4. Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, United States
5. Materials Science and Engineering Program, University of Colorado, Boulder, Colorado 80309, United States