1. Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and TechnologySouth China Academy of Advanced OptoelectronicsSouth China Normal University Guangzhou 510006 China
2. Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper DisplaysSouth China Academy of Advanced OptoelectronicsSouth China Normal University Guangzhou 510006 China
3. Key Laboratory of Theoretical Chemistry of EnvironmentMinistry of EducationSchool of ChemistrySouth China Normal University Guangzhou 510006 P. R. China
4. Institute of Polymers and Energy ChemistryCollege of ChemistryNanchang University Nanchang 330031 China
5. Laboratory of Solid State MicrostructuresNanjing University Nanjing 210093 China
6. Department of PhysicsBoston College Chestnut Hill MA 02467 USA