1. Photovoltaic Materials Group Center for Green Research on Energy and Environmental Materials National Institute for Materials Science (NIMS) 1-2-1 Sengen Tsukuba 305-0047 Japan
2. Department of Energy & Materials Engineering Research Center for Photoenergy Harvesting & Conversion Technology (phct) Dongguk University Seoul 100-715 Republic of Korea
3. Research Center for Photovoltaics (RCPV) National Institute of Advanced Industrial Science and Technology (AIST) Ibaraki 305-8565 Japan