1. Department of Electronic and Electrical Engineering, Sungkyunkwan University, 300 Chunchun-Dong, Suwon 440-746, Republic of Korea
2. Fraunhofer-Allianz Energie, Fraunhofer Institut, HeidenhofstrBe 2, 79110 Freiburg, Germany
3. Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan
4. School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052, Australia
5. Department of Materials Science and Engineering, Korea University, Anam-Dong 5-1, Seongbuk-Gu, Seoul 136-713, Republic of Korea