1. State Key Laboratory of Silicon MaterialsMOE Key Laboratory of Macromolecular Synthesis and FunctionalizationDepartment of Polymer Science and EngineeringZhejiang University Hangzhou 310027 P. R. China
2. Department of PhysicsChemistry and Biology (IFM)Linköping University Linköping 581 83 Sweden
3. School of Chemistry and Chemical EngineeringCenter for Advanced Electronic Materials and DevicesShanghai Jiao Tong University Shanghai 200240 P. R. China
4. Department of PhysicsChinese University of Hong Kong New Territories Hong Kong 999077 P. R. China
5. Department of ChemistryZhejiang University Hangzhou 310027 P. R. China