1. Center for Polymers and Organic Solids, Department of Physics, and Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
2. Makromolekulare Chemie, Bergische Universität Wuppertal, D-42097 Wuppertal, Germany
3. Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China