1. Department of New Energy Materials and Devices State Key Laboratory of Reliability and Intelligence of Electrical Equipment School of Materials Science and Engineering Hebei University of Technology Tianjin 300130 P. R. China
2. Department of Chemistry College of Chemistry and Molecular Engineering Peking University Beijing 100871 P. R. China
3. State Key Laboratory for Macroscopic Physics and Department of Physics Peking University Beijing 100871 P. R. China