1. College of Physics and Optoelectronic EngineeringShenzhen University Shenzhen 518060 P. R. China
2. Key Laboratory of Materials Processing and Mold of Ministry of EducationNational Engineering Research Center for Advanced Polymer Processing TechnologySchool of Physics and EngineeringZhengzhou University Zhengzhou 450001 P. R. China
3. CAS Center for Excellence in NanoscienceBeijing Key Laboratory of Micro-nano Energy and SensorBeijing Institute of Nanoenergy and NanosystemsChinese Academy of Sciences Beijing 100083 P. R. China
4. Center on Nanoenergy ResearchSchool of Physical Science and TechnologyGuangxi University Nanning Guangxi 530004 P. R. China