1. Guangdong Provincial Key Laboratory of Optical Information Materials and Technology and Institute of Electronic Paper Displays South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, P. R. China
2. National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou 510006, P. R. China
3. Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh 221005, India
4. Van’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Research Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands