1. Department of Electrical and Electronic Engineering; the University of Hong Kong; Hong Kong SAR China
2. State Key Laboratory on Integrated Optoelectronics; College of Electronic Science and Engineering; Jilin University; 2699 Qianjin Street Changchun 130012 PR China
3. State Key Laboratory of Inorganic Synthesis and Preparative Chemistry; College of Chemistry; Jilin University; Changchun 130012 PR China