[1] Jinan Univ, Guangdong Prov Engn Technol Res, Siyuan Lab, Dept Phys,Ctr Vacuum Coating Technol & New Energy, Guangzhou 510632, Guangdong, Peoples R China
[2] Xidian Univ, Guangzhou Inst Technol, Guangzhou 510555, Guangdong, Peoples R China
[3] Chinese Acad Sci, Beijing Inst Nanoenergy & Nanosyst, CAS Ctr Excellence Nanosci, Beijing Key Lab Micronano Energy & Sensor, Beijing 100083, Peoples R China
[4] Georgia Inst Technol, Sch Mat Sci & Engn, Atlanta, GA 30332 USA