1. Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
2. School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
3. Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
4. Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea
5. Key Laboratory of Advanced Display and System Applications Ministry of Education, Shanghai University, Yanchang Road 149, Shanghai 200072, China