1. State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques School of Materials Science and Engineering South China University of Technology Guangzhou 510641 China
2. Department of Chemistry and Applied Biosciences Institute of Inorganic Chemistry ETH Zürich Zürich 8093 Switzerland
3. Empa‐Swiss Federal Laboratories for Materials Science and Technology Dübendorf 8600 Switzerland
4. School of Physics and Optoelectronics South China University of Technology Guangzhou Guangdong 510641 China