1. National Renewable Energy Laboratory, Golden, Colorado 80401, United States
2. State Key
Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
3. Synergetic Innovation Center of Quantum Information and
Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
4. Laboratory of Nanotechnology, IMTEK, Albert Ludwigs University, Freiburg 79110, Germany
5. Renewable
and Sustainable Energy Institute, University of Colorado, Boulder, Colorado 80309, United States