1. Key Laboratory of Organic Solids, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China, Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China, School of Physical Science and Technology, Suzhou University, Suzhou 215006, P.R. China, and Department of Physics, Harbin Institute of Technology, Harbin 150001, P.R. China