1. Department of Materials Science and Engineering City University of Hong Kong Kowloon 999077 Hong Kong
2. Hong Kong Institute for Clean Energy City University of Hong Kong Kowloon 999077 Hong Kong
3. Department of Chemistry City University of Hong Kong Kowloon 999077 Hong Kong
4. Department of Physics and Organic and Carbon Electronics Laboratories (ORaCEL) North Carolina State University Raleigh NC 27695 USA
5. Department of Chemistry Hubei Key Lab on Organic and Polymeric Optoelectronic Materials Wuhan University Wuhan 430072 China
6. Department of Chemistry University of Washington Seattle WA 98195‐2120 USA
7. Department of Chemistry and the Materials Research Center Northwestern University Evanston IL 60208 USA
8. Department of Materials Science and Engineering University of Washington Seattle WA 98195‐2120 USA