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Semitransparent quantum dot light-emitting diodes by cadmium-free colloidal quantum dots

: Kim, Y.; Ippen, C.; Greco, T.; Oh, M.S.; Han, C.J.; Lee, J.; Wedel, A.; Kim, J.


Journal of nanoscience and nanotechnology 14 (2014), Nr.11, S.8636-8640
ISSN: 1533-4880
Fraunhofer IAP ()

The InP/ZnSe/ZnS multishell colloidal quantum dots (QDs) were prepared by convenient heating-up method for an emission layer of semitransparent quantum dot light-emitting diodes (QD-LEDs). The synthesized InP/ZnSe/ZnS multishell QDs exhibited an emission peak at 545 nm for clear green color with a full-width at half-maximum (FWHM) of 50 nm, and photoluminescent (PL) quantum yield (QY) of 45%. The multishell on the indium phosphide (InP) core helped increasing QY and stability by reducing interfacial defects. Using a Ca/Ag cathode, the whole QD-LEDs were semitransparent throughout the visible wavelengths. The maximum brightness and currernt efficiency of semitransparent QD-LEDs reached 587 cd/m(2) and 1.52 cd/A by controlling the thickness of Ca/Ag cathode, which is comparable to the device with opaque LiF/Al cathode (1444 cd/m(2) and 1.98 cd/A). The performance of our semitransparent and eco-friendly device is not matched with traditional cadmium (Cd) based QD-LEDs yet, but it shows the great potential for various window-type information displays.