1. Department of Physics, Renewable Energy Materials Research Science and Engineering Center, Colorado School of Mines, Golden, Colorado 80401, United States
2. Department of Chemical Engineering, Renewable Energy Materials Research Science and Engineering Center, Colorado School of Mines, Golden, Colorado 80401, United States
3. National Renewable Energy Laboratory, Golden, Colorado 80401, United States
4. Materials Research Institute, Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States