1. Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520, United States
2. Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, United States
3. Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, United States
4. Department of Physics, Chonnam National University, Gwangju 61186, Republic of Korea
5. Electronic and Optoelectronic System Research Laboratories, Industrial Technology Research Institute ITRI, Hsinchu 31057, Taiwan