1. School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, P. R. China
2. Chongqing Research Institute, Changchun University of Science and Technology, Chongqing 401135, P. R. China
3. Engineering Research Center for Optoelectronic Functional Materials, Ministry of Education, Changchun 130022, P. R. China
4. State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, P. R. China