1. Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore
2. Department of Physics Southern University of Science and Technology (SUSTech) No. 1088, Xueyuan Rd Shenzhen 518055 Guangdong P. R. China
3. College of Chemistry Nankai University Tianjin 300071 P. R. China
4. ARC Centre of Excellence in Exciton Science School of Chemistry The University of Sydney NSW 2006 Australia
5. MajuLab CNRS‐Université de Nice‐NUS‐NTU International Joint Research Unit UMI 3654 Singapore 637371 Singapore
6. The Photonics Institute and Centre for Disruptive Photonic Technologies Nanyang Technological University Singapore 637371 Singapore