1. School of Materials Science and Engineering, Chang’an University, Xi’an, P. R. China
2. State Key Laboratory of Fluorine & Nitrogen Chemicals, Xi’an, P. R. China
3. Xi’an Key Laboratory of Liquid Crystals and Organic Photovoltaic Materials, Xi’an, P. R. China
4. Optical and Electrical Material Center, Xi’an Modern Chemistry Research Institute, Xi’an, P. R. China