Near-white emitting QD-LED based on hydrophilic CdS nanocrystals

Molaei, M ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1016/j.jlumin.2011.08.038
  3. Abstract:
  4. In this work we report fabrication of a nanocrystal (NC)-based hybrid organicinorganic LED with structure of ITO/PEDOT:PSS/PVK/CdS-NCs/(Al or Mg:Ag). The hydrophilic CdS NCs were synthesized using a novel aqueous thermochemical method at 80 °C and sizes (around 2 nm) were controlled by thioglycolic acid (TGA) as the capping agent. The favorite feature of these NCs is their relatively high emission intensity and broad, near-white emission. The hydrophilic CdS NCs were successfully spin coated using Triton X-100 as the wetting agent. The fabricated LEDs demonstrated a turn on voltage about 7 V for Al metallic contact. The electroluminescence was a broad spectrum at 540 and 170 nm width, which was about 50 nm red shifted compared to photoluminescence spectra. The CIE color coordinates of the LED at (0.33, 0.43) demonstrated a near white light LED with an emission on greenyellow boundary of white. Annealing of the device up to 190 °C had a positive effect on the performance, possibly due to better contacts between layers. Replacing Al contacts with Mg:Ag reduced the turn-on voltage to 6 V and changed CIE color coordinate to (0.32, 0.41). The EL peak was also shifted to 525 nm, with a brightness of 15 Cd/m2 at working voltage of 15 V. The current efficiency and external quantum efficiency of device were 0.08 Cd/A and 0.03% at current densities higher than 10 mA/cm2
  5. Keywords:
  6. White emission ; Aqueous synthesis ; CdS nanocrystals ; Hydrophilic ; QD-LED ; White emissions ; Aluminum ; Cadmium compounds ; Cadmium sulfide ; Electroluminescence ; Hydrophilicity ; Nanocrystals ; Photoluminescence ; Silver ; Surface active agents ; Light emitting diodes
  7. Source: Journal of Luminescence ; Volume 132, Issue 2 , 2012 , Pages 467-473 ; 00222313 (ISSN)
  8. URL: http://www.sciencedirect.com/science/article/pii/S0022231311004856