1. Institute for Advanced Materials Guangdong Provincial Key Laboratory of Optical Information Materials South China Academy of Advanced Optoelectronics South China Normal University Guangzhou 510006 P. R. China
2. Institute of Electronic Paper Displays Guangdong Provincial Key Laboratory of Optical Information Materials South China Academy of Advanced Optoelectronics South China Normal University Guangzhou 510006 P. R. China
3. Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures Nanjing University Nanjing 21009 P. R. China