1. College of Chemistry and Environmental ScienceKey Laboratory of Chemical Biology of Hebei ProvinceKey Laboratory of Medicinal Chemistry and Molecular Diagnosis, Ministry of EducationHebei University Baoding 071002 P.R. China
2. Department of PhysicsHarbin Institute of Technology Harbin 150001 P.R. China
3. Institution National–Local Joint Engineering Laboratory of, New Energy Photovoltaic DevicesCollege of Physics Science and TechnologyHebei University Baoding 071002 P.R. China