1. Department of Physics, University of Colorado, Boulder, Colorado 80309, United States
2. Department of Electrical, Computer and Energy Engineering, University of Colorado, Boulder, Colorado 80309, United States
3. Soft Materials Research Center and Materials Science and Engineering Program, University of Colorado, Boulder, Colorado 80309, United States
4. Chemical Physics Program, Departments of Chemistry and Physics, University of Colorado, Boulder, Colorado 80309, United States
5. Renewable and Sustainable Energy Institute, National Renewable Energy Laboratory and University of Colorado, Boulder, Colorado 80309, United States