1. Centre for Advanced Optoelectronic Functional Materials Research and Key Laboratory of UV-Emitting Materials and Technology; Ministry of Education; Northeast Normal University; Changchun 130024 China
2. National Demonstration Center for Experimental Physics Education; Northeast Normal University; Changchun 130024 China
3. Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education; Jilin Normal University; Changchun 130103 China