Recently, cesium lead halide (CsPbX3) perovskite quantum dots (QDs) have attracted much attention because of their excellent optical properties in terms of quantum yield of >85% and full width at half maximum of 25nm (Figure 1). The Cd-free technology has been proposed for the use in backlight films as an alternative to current CdSe and InP based systems.
Present results show that the cesium lead halide QDs can also be used in a pixelated color conversion layer. The CsPbX3 materials possess exceptional absorption properties making them favorable for the use as a color converter. RoHS (Restriction of Hazardous Substances) compliant green and red QD layers, containing less than 1000 ppm Pb, exhibit > 90% conversion at a layer thickness of less than 500 microns (Figure 2).
In the proposed architecture, the blue light of selected pixels (a pixel is the smallest addressable element in an all points addressable display device) is converted into green or red light, respectively. Possible applications include OLED displays or LCD displays (Figure 3).
This technology has the potential to substantially reduce the energy consumption of a TV. No color filters would be needed in such devices and hence no light would be absorbed in the filter. Thus, the energy consumption of todays TVs could be reduced to about one third.
Figure 1: Cadmium-free, high performing QDs with different emission peak wavelength.
Figure 2: Spectra of green and red conversion layer of thickness 400 microns upon excitation by a blue backlight unit of a commercial TV set (excitation ~450nm). The Pb content is 800ppm for the green layer and 100ppm for the red layer, respectively.
Figure 3: Example of the architecture of red, green and blue pixels using CsPbX3 QD color conversion layers. The concept can be used in OLED or LCD displays.
This information has been sourced, reviewed and adapted from materials provided by Nanograde Ltd - Nanoparticle Dispersions.
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