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Why are quantum dots concerned by academic and industrial technology researchers?

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Time of issue:2019-03-21
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(Summary description)White light LEDs have been widely used in people’s lives. The white light source combined with blue LEDs and down-conversion fluorescent materials. This spectrally adjustable white light solution has been applied to many consumer products, no matter from the backlight of liquid crystal display panels. Source to LED lighting bulb. With the improvement of market demand and technological innovation, LED white light sources have changed from the initial pursuit of high efficiency and high brightness to controllable light and higher color quality. For down-conversion fluorescent materials, we introduce some new technology directions related to LED display and lighting. Understand why we should use quantum dots as the next generation of light conversion materials in LED display and lighting.

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Why are quantum dots concerned by academic and industrial technology researchers?

Categories:Company News
Author:
Origin:
Time of issue:2019-03-21
Views:0

Information

White light LEDs have been widely used in people’s lives. The white light source combined with blue LEDs and down-conversion fluorescent materials. This spectrally adjustable white light solution has been applied to many consumer products, no matter from the backlight of liquid crystal display panels. Source to LED lighting bulb. With the improvement of market demand and technological innovation, LED white light sources have changed from the initial pursuit of high efficiency and high brightness to controllable light and higher color quality. For down-conversion fluorescent materials, we introduce some new technology directions related to LED display and lighting. Understand why we should use quantum dots as the next generation of light conversion materials in LED display and lighting.

High-quality lighting

Traditional LED lighting is generally white light composed of blue LED combined with YAG phosphor, which has the advantages of high light efficiency and low cost. However, there is still a certain gap between its spectrum and the sunlight that people are accustomed to. The direction of improving the color rendering index is mainly to add a variety of down-conversion fluorescent materials, such as a variety of color broad-spectrum phosphors, to make the LED white light spectrum closer to the full spectrum. range. However, some people did the opposite, trying to use a narrow half-width multi-color laser combination as a white light source to test whether it can be accepted by people.

Researcher J.Y. Tsao from Sandia National Laboratory (SNL) of the US Department of Energy used four colors of blue, green, yellow, and red lasers to form a white light source.

Figure 1: Schematic diagram of four-color laser white light illumination

The team is curious whether the white light of diode lasers will affect the human eye, unlike the white light produced by LEDs. To test this question, the researchers conducted a series of tests at the High-Tech Materials Center of the University of New Mexico. By comparing the four-color laser with the incandescent lamp, and passing the blind selection test of forty volunteers, the volunteers did not have a significant preference for the choice of light source, which means that the laser as a white light source has the high-definition characteristics of traditional incandescent lamps. The color index is not obvious to people as lighting users. This research result is very valuable for us to use the narrow peak width spectrum combination as a white light source.

Wide color gamut display

Liquid crystal display technology based on LED backlight is currently the mainstream in the TV and mobile phone markets. As a white light source, LEDs need to undergo various processes to form RGB pixels to produce images that can be perceived by humans.

Figure 2: Schematic diagram of LCD TV disassembly

The pixels of different colors are mainly realized by the backlight light source combined with the filter. I will not go into it here, we have the opportunity to introduce it in detail. Traditional phosphors have a wide half-width, and the excess spectral energy will be absorbed after passing through the filter. This not only causes a drop in efficiency, but the half-width of the spectrum through the filter is also wider. The color gamut coverage area is not light enough. As shown in the figure below, if we have a narrow half-width spectrum such as red, green, and blue light at 24nm, most of their spectrum can pass directly through the filter, and its color gamut can greatly exceed the NTSC standard.

Figure 3: Quantum dots and different half-width color gamut areas

Speaking of this, some people may have found that around high-quality lighting and wide color gamut display, an important parameter is mentioned, that is, a narrow half-width spectrum. The particle size of Quantum Dots materials is generally between 1-10nm. Because electrons and holes are quantum confined, the continuous band structure becomes a discrete level structure, so the emission spectrum is very narrow (20-30nm). ), the chromaticity is high, the color gamut is wide, which can greatly exceed the color gamut of NTSC (>100%); at the same time, the light absorption loss through the color filter is small, and low power consumption can be realized. Due to the quantum confinement effect, the same material only needs to change the size of the quantum dot particles to cover the entire visible spectrum. A variety of quantum dots of different sizes can be mixed in a certain ratio to achieve a natural light color similar to sunlight and obtain a higher color rendering index. Because of the above characteristics, quantum dots have attracted the attention of academic and industrial technology researchers.

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