1. Institute of Electronic Paper Displays South China Academy of Advanced Optoelectronics South China Normal University Guangzhou Guangdong Province 510006 China
2. Institute of Polymer Optoelectronic Materials and Devices State Key Laboratory of Luminescent Materials and Devices South China University of Technology Guangzhou 510640 P. R. China
3. Materials Sciences Division Lawrence Berkeley National Lab Berkeley CA 94720 USA
4. Polymer Science and Engineering Department University of Massachusetts Amherst MA 01003 USA
5. Department of Physics and Astronomy, and Collaborative Innovation Center of IFSA (CICIFSA) Shanghai Jiaotong University Shanghai 200240 P. R. China
6. Shenzhen Guohua Optoelectronics Tech. Co. Ltd. Shenzhen 518110 P. R. China
7. Academy of Shenzhen Guohua Optoelectronics Shenzhen 518110 P. R. China