Affiliation: | a Structure Research Laboratory, University of Science and Technology of China, Academia Sinica, 230026 Hefei, Anhui, PR China b Department of Physics, University of Science and Technology of China, 230026 Hefei, Anhui, PR China c Laboratoire des Physico-Chimie des Materiaux Luminescents, CNRS-UMR 5620, Universite Claude Bernard Lyon I, 43 Boulevard du 11 Novembre 1918, 69622, Villeurbanne Cedex, France |