1. The Hong Kong University of Science and Technology-Shenzhen Research Institute; No. 9 Yuexing 1st RD, Hi-tech Park Nanshan Shenzhen 518057 China
2. Department of Chemistry and Energy Institute; The Hong Kong University of Science and Technology; Clear Water Bay Hong Kong
3. Department of Physics and Organic and Carbon Electronics Laboratory; North Carolina State University; Raleigh NC 27695 USA
4. State Key Laboratory for Mechanical Behavior of Materials; Xi'an Jiaotong University; Xi'an 710049 China