1. Department of Materials Science and Engineering University of Washington Seattle WA 98195 USA
2. State Key Laboratory of Luminescent Materials and Devices Institute of Polymer Optoelectronic Materials and Devices South China University of Technology 381 Wushan Road Guangzhou 510640 China
3. Department of Physics and Astronomy Shanghai Jiaotong University Shanghai 200240 China
4. Department of Chemistry University of Washington Seattle WA 98195 USA
5. Department of Chemistry City University of Hong Kong Kowloon 999077 Hong Kong