[1] Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
[2] Department of Physics, University of California, Berkeley,CA94720, United States
[3] Institute of Advanced Energy, Kyoto University, Kyoto, Uji,611-0011, Japan
[4] Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley,CA,94720, United States
[5] Institute of Experimental and Applied Physics, University of Regensburg, Regensburg,93053, Germany
[6] Institute for Functional Intelligent Materials, National University of Singapore, Singapore
[7] Joint School, National University of Singapore, Tianjin University, International Campus of Tianjin University, Fuzhou,350207, China