1. Department of Macromolecular Science, State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200438, China
2. Department of Science and Technology, Laboratory of Organic Electronics, Linköping University, Norrköping, 60174 Sweden
3. Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala, SE-751 20, Sweden
4. Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China