1. SPECIFIC, Faculty of Science and Engineering Swansea University Bay Campus, Fabian Way Swansea SA1 8EN United Kingdom
2. Department of Physics City University of Hong Kong Kowloon Hong Kong SAR China
3. School of Semiconductor Science and Technology South China Normal University Foshan Guangdong 528225 China
4. State Key Laboratory of Luminescent Materials and Devices South China University of Technology 381 Wushan Road Guangzhou Guangdong 510640 China
5. Department of Materials Science and Engineering City University of Hong Kong Kowloon Hong Kong, China
6. School of Energy and Environment City University of Hong Kong Kowloon Hong Kong, China
7. Hong Kong Institute for Clean Energy City University of Hong Kong Kowloon Hong Kong, China