1. Hydrogen·Fuel Cell Research Center Korea Institute of Science and Technology (KIST) Seoul 02792 Republic of Korea
2. Advanced Photovoltaics Research Center KIST Seoul 02792 Republic of Korea
3. Graduate School of Energy and Environment (KU-KIST Green School) Korea University Seoul 02841 Republic of Korea
4. Division of Energy-Environment Engineering KIST School University of Science and Technology (UST) Daejeon 34113 Republic of Korea
5. School of Materials Science and Engineering Georgia Institute of Technology Atlanta Georgia 30332 USA