[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