1. Department of Electrical Engineering; Korea Advanced Institute of Science and Technology (KAIST); Daejeon 305 - 701 Republic of Korea
2. Department of Physics; Korea Advanced Institute of Science and Technology (KAIST); Daejeon 305 - 701 Republic of Korea
3. OLED Research Center; Electronics and Telecommunications Research Institute (ETRI); Daejeon 305-700 Republic of Korea