Seminar Series:
Yassamin GhafouriUniversity of Georgia, Department of Chemistry
Monday, November 13, 2017 - 11:15am
Chemistry Building, Room 400

Traditional lighting methods such as incandescent and fluorescent bulbs utilize less than 30% of the energy input to produce light while roughly 70% is dissipated as heat. This technology is not only cost inefficient but also environmentally harmful.1 The demand for more sustainable and efficient lighting has led to unparalleled interest in the devolvement of light emitting diodes or LEDs. These LEDs are much brighter, have longer operational lifetimes, and higher energy conversion rates compared to traditional lighting.2 The newest class of LEDs makes use of a nanocrystal quantum dot emissive layer sandwiched between charge transporting materials. These quantum dot light emitting diodes (QDLED) have shown great promise with external quantum efficiencies (EQE) improving from 0.2% to 20.5%.3  However, one of the challenges to producing high performances QDLEDs is charge balance.  An imbalance of charge within the LED increases nonradiative Auger recombination lowering efficiency and operational lifetime.4 This talk will present recent research with specific focus on the accumulation of charge and suppression of Auger recombination through methods such as modification of quantum dot structure,5  ligand exchange,6 and device engineering.7

  1. Bae, W. K.; Brovelli, S.; Klimov, V. I. MRS Bull. 2013, 38, 721−730.
  2. Pimputkar, S.; Speck, J.; Denbaars, S.; Nakamura, S., Nat Photonics 2009, 3, 180-182.
  3. Shang, Y.; Ning, Z. Nat. Sci. Rev. 2017, 4, 170-183.
  4. Oron, D.; Kazes, M.; Banin, U. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 75, 035330−035337.
  5. Wan Ki Bae, Lazaro A. Padilha, Young-Shin Park, Hunter McDaniel, Istvan Robel, Jeffrey M. Pietryga, and Victor I. Klimov. ACS Nano. 2013, 7, 3411-3419
  6. Ikjun Cho, Heeyoung Jung, Byeong Guk Jeong, Jun Hyuk Chang, Younghoon Kim, Kookheon Char, Doh C. Lee, Changhee Lee, Jinhan Cho, and Wan Ki Bae. ACS Nano. 2017, 11, 684-692
  7. Dai, X.; Zhang, Z.; Jin, Y.; Niu, Y.; Cao, H.; Liang, X.; Chen, L.; Wang, J.; Peng, X. Nature. 2014, 515 (7525), 96-99.