1. Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering, Ministry of Education, Tsinghua University, Beijing 100084, China
2. Shanghai
Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
3. Department
of Chemistry, Brown University, Providence, Rhode Island 02912, United States
4. Physical
and Theoretical Chemistry, University of Siegen, Siegen 57068, Germany