1. Department of Chemistry, Research Institute for Natural Sciences, Korea University, 5 Anam-dong, Seongbuk-gu, Seoul 136-701, Korea
2. Photo-electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul 02792, Korea
3. Department of Information Display, Kyung Hee University, 26, Kyungheedae-ro, Dongdaemun-gu, Seoul 02447, Korea