1. Department of PhysicsSiyuan LaboratoryGuangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Energy MaterialsJinan University Guangzhou Guangdong 510632 P. R. China
2. Institute for Solar Energy SystemsGuangdong Provincial Key Laboratory of Photovoltaic Technology School of PhysicsSun Yat-Sen University Guangzhou Guangdong 510006 P. R. China
3. Electronic Information DepartmentFoshan Polytechnic Foshan Guangdong 528131 P. R. China