1. School of Materials Science and Engineering; Gwangju Institute of Science & Technology (GIST); Gwangju 61005 Republic of Korea
2. School of Electrical and Electronic Engineering; Yonsei University; Seoul 03722 Republic of Korea
3. KEPCO Research Institute; Korea Electric Power Corporation; Naju 58214 Republic of Korea
4. Department of Materials Science and Engineering; Yonsei University; Seoul 03722 Republic of Korea
5. Department of Energy Science; Sungkyunkwan University; Suwon 16419 Republic of Korea