1. Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Organic Solids; Institute of Chemistry; Chinese Academy of Sciences; Beijing 100190 P. R. China
2. Department of Energy Conversion and Storage; Technical University of Denmark; Roskilde DK-4000 Denmark
3. University of Chinese Academy of Sciences; Beijing 100049 P. R. China
4. Department of Polymer Science and Engineering; Zhejiang University; Hangzhou 310027 P. R. China
5. Department of Materials Science and Engineering; College of Engineering; Key Laboratory of Polymer Chemistry and Physics of Ministry of Education; Peking University; Beijing 100871 P. R. China