1. State Key Laboratory of Metal Matrix CompositesShanghai Jiao Tong University 800 Dong Chuan Road Shanghai 200240 China
2. Photovoltaic Materials Group, Center for Green Research on Energy and Environmental MaterialsNational Institute for Materials Science Tsukuba Ibaraki 305-0047 Japan
3. Research Center for Advanced Science and TechnologyUniversity of Tokyo Tokyo 153-8904 Japan
4. School of Materials Science and EngineeringHenan Institute of Advanced TechnologyZhengzhou University Zhengzhou 450001 China