1. Key Laboratory of Luminescence and Optical Information Ministry of Education Beijing Jiaotong University 100044 Beijing P. R. China
2. Center for Excellence in Nanoscience (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS) National Center for Nanoscience and Technology 100190 Beijing P. R. China
3. Department of Physics Beijing Technology and Business University 100048 Beijing P. R. China
4. Key Lab for Special Functional Materials Ministry of Education National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology School of Materials Henan University 475004 Kaifeng P. R. China
5. Organic Optoelectronic Materials Laboratory Department of Chemistry College of Science Korea University 02841 Seoul Republic of Korea
6. Institute for Display and Sensor Devices BOE Technology Group Co. Ltd. No. 9 Dize Road, BDA Beijing 100176 P. R. China