1. Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Shanghai Key Laboratory of Functional Materials Chemistry, School of Chemistry and Molecular Engineering, East China University of Science & Technology, Shanghai 200237, P. R. China
2. Department of Science and Technology, Laboratory of Organic Electronics, Linköping University, Norrköping 60174, Sweden
3. Department of Physics and Astronomy, Uppsala University, Uppsala 751 20, Sweden