1. School of Physics State Key Laboratory of Crystal Materials Shandong University Jinan Shandong 250100 P. R. China
2. Henan Key Laboratory of Infrared Materials & Spectrum Measures and Applications Henan Normal University Xinxiang Henan 453007 P. R. China
3. Shanghai Synchrotron Radiation Facility (SSRF) Zhangjiang Laboratory Shanghai Advanced Research Institute Chinese Academy of Sciences 239 Zhangheng Road Shanghai 201204 P. R. China
4. ARC Centre of Excellence in Exciton Science School of Chemistry The University of Melbourne Parkville Victoria 3010 Australia