1. State Key Laboratory of Polymer Physics and Chemistry; Changchun Institute of Applied Chemistry; University of Chinese Academy of Sciences; Changchun 130022 P. R. China
2. Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials; Hubei Key Lab on Organic and Polymeric Optoelectronic Materials; Department of Chemistry; Wuhan University; Wuhan 430072 P. R. China
3. Organic Photonics and Electronics Group; Department of Physics; Umeå University; SE-901 87 Umeå Sweden
4. Institute of Polymer Optoelectronic Materialsand Devices; State Key Laboratory of Luminescent Materials and Devices; South China University of Technology; Guangzhou 510640 P. R. China