1. Department of Materials Science and Engineering; City University of Hong Kong; 83 Tat Chee Avenue Hong Kong SAR China
2. City University of Hong Kong Shenzhen Research Institute; Shenzhen 518057 China
3. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province; College of Optoelectronic Engineering; Shenzhen University; Shenzhen 518060 China
4. Department of Applied Biology and Chemical Technology; The Hong Kong Polytechnic University; Hung Hom, Kowloon Hong Kong SAR China