1. Center of Materials Science and Optoelectronics Engineering College of Materials Science and Opto-Electronic Technology & CAS Center for Excellence in Topological Quantum Computation & CAS Key Laboratory of Vacuum Physic University of Chinese Academy of Sciences Beijing 100049 P. R. China
2. Key Laboratory of Organic Solids Beijing National Laboratory for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 100190 P. R. China
3. Beijing Key Laboratory for Optical Materials and Photonic Devices Department of Chemistry Capital Normal University Beijing 100048 P. R. China
4. State Key Laboratory of Luminescent Materials and Devices School of Materials Science and Engineering South China University of Technology Guangzhou 510640 P. R. China
5. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics Georgia Institute of Technology Atlanta GA 30332 USA
6. Department of Chemistry Emory University Atlanta GA 30322 USA