1. Department of Electronic Materials Engineering; Kwangwoon University; 447-1, Wolgye-dong Nowon-gu Seoul 139-701 Korea
2. Material Techonology Center; Korea Testing Laboratory; 222-13, Guro3-dong Guro-gu Seoul 152-718 Korea
3. Solar Cell Laboratory; LG Innotek Co., Ltd.; Osan 447-705 Korea
4. School of Materials Science and Engineering; Pusan National University; Busan 609-309 Korea