1. State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials; South China University of Technology; Guangzhou 510641 China
2. Department of Physics; South China University of Technology; Guangzhou 510641 China
3. Otto Schott Institute of Materials Research; University of Jena; 07743 Jena Germany
4. Center for Energy and Environmental Chemistry; University of Jena; 07743 Jena Germany