1. State Key Laboratory of Luminescent Materials and DevicesSouth China University of Technology 381 Wushan Road Guangzhou 510640 P. R. China
2. Department of Materials Science and EngineeringUniversity of Washington Seattle WA 98195‐2120 USA
3. Department of Physics and Astronomy, and Collaborative Innovation Center of IFSA (CICIFSA)Shanghai Jiaotong University Shanghai 200240 P. R. China
4. South China Normal University Guangzhou 510006 P. R. China
5. College of ChemistryNankai University Tianjin 300071 China
6. Polymer Science and Engineering DepartmentUniversity of Massachusetts Amherst MA 01003 USA
7. Materials Sciences DivisionLawrence Berkeley National Lab Berkeley CA 94720 USA
8. Department of Materials Science and EngineeringCity University of Hong Kong Kowloon Hong Kong 999077 China