1. Department of Physics; The University of Hong Kong; Pokfulam Road Hong Kong SAR
2. Department of Materials Science and Engineering; Shenzhen Key Laboratory of Full Spectral Solar Electricity Generation (FSSEG); Southern University of Science and Technology; No. 1088, Xueyuan Rd. Shenzhen 518055 Guangdong P. R. China
3. Materials Characterization and Preparation Center (MCPC); Department of Physics; Southern University of Science and Technology of China; Shenzhen 518055 China
4. Department of Electronic and Information Engineering; The Hong Kong Polytechnic University; Hung Hom Kowloon Hong Kong SAR
5. Department of Chemistry; The University of Hong Kong; Pokfulam Road Hong Kong SAR