1. Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 101400, China.
2. School of Nanoscience and Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
3. School of Integrated Circuits and Beijing National Research Center for Information Science and Technology, Tsinghua University, Beijing 10084, China.
4. The University of Manchester, Manchester M13 9PL, UK.
5. Centre for Photonic Devices and Sensors, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK.
6. Guangzhou Institute of Blue Energy, Knowledge City, Huangpu District, Guangzhou 510555, China.
7. Georgia Institute of Technology, Atlanta, GA 30332-0245, USA.