1. Key Laboratory of Organic Optoelectronics & Molecular Engineering Ministry of Education Department of Chemistry and State Key Laboratory of Tribology Department of Mechanical Engineering Tsinghua University Beijing 100084 P. R. China
2. Applied Mechanics Laboratory Department of Engineering Mechanics and Center for Nano and Micro Mechanics Tsinghua University Beijing 100084 P. R. China
3. State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011‐Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 P. R. China
4. Laboratory of Flexible Electronics Technology Tsinghua University Beijing 100084 P. R. China