1. China-German
Research Center for Photonic Materials and Devices, the State Key
Laboratory of Luminescent Materials and Devices, School of Materials
Science and Engineering, South China University of Technology, Guangzhou 510641, China
2. Department
of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China
3. Otto
Schott Institute of Materials Research, University of Jena, 07743 Jena, Germany