1. Department of Chemistry City University of Hong Kong Kowloon 999077 Hong Kong
2. Department of Materials Science and Engineering City University of Hong Kong Kowloon 999077 Hong Kong
3. School of Materials Science and Engineering Xi'an University of Science and Technology Xi'an 710054 P. R. China
4. Department of Materials Science and Engineering University of Washington Box 352120 Seattle WA USA
5. The Institute for Advanced Studies Wuhan University Wuhan 430072 China
6. Department of Chemistry College of Science Korea University Seoul 136‐713 Republic of Korea
7. Department of Chemistry Hubei Key Lab on Organic and Polymeric Optoelectronic Materials Wuhan University Wuhan 430072 China