1. Heeger Center for Advanced Materials; Research Institute for Solar & Sustainable Energies; Gwangju Institute of Science & Technology; Gwangju 500-712 Republic of Korea
2. Advanced Photonics Research Institute; Gwangju Institute of Science & Technology; Gwangju 500-712 Republic of Korea
3. School of Materials Science & Engineering; Gwangju Institute of Science & Technology; Gwangju 500-712 Republic of Korea