Fig. 7: Mixing multi-colour QDs as a monolayer for SEL-WQLEDs.

a Atomic force microscopy phase image of blue QDs forming approximately 1.1 monolayers on top of a 40-nm-thick TPD film and device cross section of a white QD–LED. b Normalised EL spectra of a white QD–LED for a set of increasing applied voltages. The relative intensities of the red and blue QD spectral components increase in comparison to the green QD component at higher biases. c CIE coordinates with the red, green, and blue QD–LEDs (triangles). The circle symbols show the evolution of the CIE coordinates and CRI of the white QD–LEDs upon increasing the applied bias. Reprinted with permission from ref. ²⁵. Copyright 2007 American Chemical Society. d Device architecture and e energy-band diagram of white QLEDs with an inverted device structure of ITO/ZnO nanoparticle films (50 nm)/mixed QD-active layers/CBP (40 nm)/MoO₃ (10 nm)/Al (100 nm). ZnO and QD layers were prepared by spin-casting, and CBP, MoO₃, and Al were thermally evaporated on top of the spin-cast ZnO/QD layers. f EQE and g EL spectra of tetrachromatic (B + C + Y + R) white QLEDs. The brightness, power efficiency, and applied voltage of white QLEDs at brightness levels of 500, 1000, and 5000 cd m⁻² are also indicated on EQE vs. J graphs. The CIE coordinate is displayed in the inset. Reprinted with permission from ref. ²². Copyright 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. h Schematic illustrating the experimental setup by blade coating. i Structure-mechanism diagram of WQLEDs. j Normalised EL spectra of white QLEDs at various voltages. k CIE coordinates of the device at various voltages; the inset is a photograph of the luminous white QLED at 8 V. Reprinted with permission from ref. ²⁴. Copyright 2020 Elsevier