1. College of Physics Science and Technology Yangzhou University Yangzhou 225002 P. R. China
2. State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials(SICAM) School of Materials Science and Engineering Nanjing University of Posts and Telecommunications Nanjing 210023 P. R. China
3. College of Physics and Hebei Advanced Thin Films Laboratory Hebei Normal University Shijiazhuang 050024 P. R. China
4. Department of Physics Yancheng Institute of Technology Yancheng Jiangsu 224051 P. R. China
5. College of Chemistry and Molecular Engineering Qingdao University of Science and Technology Qingdao 266042 (P. R. China