1. Photovoltaic Materials Group, Center for GREEN Research on Energy and Environmental Materials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
2. Flinders Institute for Nanoscale Science and Technology, Flinders University, P.O. Box 2100, Adelaide, SA 5001, Australia
3. Department of Physics, College of Science, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, 31441 City Dammam, Saudi Arabi