1. Key Laboratory for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, China
2. School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
3. National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan