1. LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronics Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 Singapore
2. Department of Electrical and Electronics Engineering, Department of Physics, and UNAM−Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
3. Department of Physics, Abant Izzet Baysal University, Bolu 14030, Turkey
4. Department of Chemistry and Vanderbilt Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee 37235, United States