1. State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials Laboratory of Advanced Optoelectronic Materials College of Chemistry Chemical Engineering and Materials Science Soochow University Suzhou 215123 China
2. Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371
3. Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
4. Department of Physics and Astronomy Shanghai Jiaotong University Shanghai 200240 China
5. CAS Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology Beijing 100190 China
6. CAS Research/Education Center for Excellence in Molecular Sciences CAS Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China