1. School of Electrical Engineering and Automation Hefei University of Technology Hefei 230009 P. R. China
2. Special Display and Imaging Technology Innovation Center of Anhui Province Academy of Opto-Electric Technology Hefei University of Technology Hefei 230009 P. R. China
3. Key Laboratory of Photovoltaic and Energy Conservation Materials Institute of Solid State Physics Hefei Institutes of Physical Science Chinese Academy of Sciences Hefei 230031 China
4. Department of Materials Science and Engineering Southern University of Science and Technology Shenzhen 518055 P. R. China