1. School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, Gwangju 61005, South Korea
2. Research Institute for Solar and Sustainable Energies, Gwangju Institute of Science and Technology, Gwangju 61005, South Korea
3. Optoelectronic Convergence Research Center, Department of Materials Science and Engineering, Chonnam National University, Gwangju 61186, South Korea