1. Department of Engineering, Electrical Engineering Division, University of Cambridge, 9 JJ Thomson Avenue, CB3 0FA, Cambridge, United Kingdom
2. Display Research Centre, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, People’s Republic of China
3. Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom
4. Department of Energy Science, Sungkyunkwan University, Suwon, 440-746, Republic of Korea
5. Department of Information Display, Kyung Hee University, Seoul 130-701, Republic of Korea