1. Ningbo Institute of Materials Technology & Engineering, Chinese Academy Sciences, Ningbo 315201, P. R. China
2. Center for Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing 100049, P. R. China
3. Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
4. Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, D-01069 Dresden, Germany
5. Organic Chemistry of Polymers, Technische Universität Dresden, 01062 Dresden, Germany