1. Department of Physics
and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606, United States
2. Key Laboratory of Artificial Micro/Nano Structures
of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, China
3. Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States