1. 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
2. College of Materials Science and Opto‐Electronic TechnologyUniversity of Chinese Academy of Science Beijing 100049 P. R. China
3. Department of Materials Science & EngineeringInha University Incheon 22212 Republic of Korea
4. Center on Nanoenergy ResearchSchool of Physical Science and TechnologyGuangxi University Nanning Guangxi 53000 P. R. China
5. School of Materials Science and EngineeringGeorgia Institute of Technology Atlanta GA 30332‐0245 USA