Saturated and multi-colored electroluminescence from quantum dots based light emitting electrochemical cells

Gang Qian, Ying Lin, Guillaume Wantz, Andrew R. Davis, Kenneth R. Carter, James J. Watkins

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

Novel light emitting electrochemical cells (LECs) are fabricated using CdSe-CdS (core-shell) quantum dots (QDs) of tuned size and emission blended with polyvinylcarbazole (PVK) and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6). The performances of cells constructed using sequential device layers of indium tin oxide (ITO), poly(3,4- ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), the QD/PVK/IL active layer, and Al are evaluated. Only color saturated electroluminescence from the QDs is observed, without any other emissions from the polymer host or the electrolyte. Blue, green, and red QD-LECs are prepared. The maximum brightness (≈1000 cd m-2) and current efficiency (1.9 cd A-1) are comparable to polymer LECs and multilayer QD-LEDs. White-light QD-LECs with Commission Internationale d'Eclairage (CIE) coordinates (0.33, 0.33) are prepared by tuning the mass ratio of R:G:B QDs in the active layer and voltage applied. Transparent QD-LECs fabricated using transparent silver nanowire (AgNW) composites as the cathode yield an average transmittance greater than 88% over the visible range. Flexible devices are demonstrated by replacing the glass substrates with polyethylene terephthalate (PET). Quantum dot based light emitting electrochemical cells are prepared by blending of quantum dots, polyvinylcarbazole and an ionic liquid. Saturated red, orange, green, blue, and white electroluminescences are demonstrated and the performance of these simple, single-layered devices is comparable to that of multilayer LED devices. Transparent and flexible devices are also demonstrated and enable a broad range of application.

Original languageEnglish (US)
Pages (from-to)4484-4490
Number of pages7
JournalAdvanced Functional Materials
Volume24
Issue number28
DOIs
StatePublished - Jul 23 2014

Keywords

  • electrochemical cells
  • flexible devices
  • quantum dots
  • saturated emission
  • white-light emission

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