Home » What are Quantum Dots and QLEDs? What do they do?

What are Quantum Dots and QLEDs? What do they do?

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What are Quantum Dots and QLEDs?
The average consumer will say.

Is QLED similar to the expensive OLED TVs? I heard from the guide that the life span is very long, and I heard that quantum dots seem to be toxic?

Consumers who know a little will say.

Quantum dot and QLED seems to be a meaning, it seems to be a wide color gamut solution, the principle or LCD TV.


Because the smart TV is not as important as cell phones and computers, so although the majority of people have a TV at home, but the people who have an understanding of television is rare, so in the face of “quantum dot TV”, “QLED TV” such terms, ordinary consumers are confused, completely unintelligible, so I first explain to you on the TV products advertised quantum dot and QLED is what, what is the use, and then spread out, so that we have a more in-depth understanding of this product.

Quantum dot and QLED, which are currently advertised on TV products, mean the same thing, referring to LCD TVs that use quantum dot material, with the aim of significantly improving the color gamut range of TVs, enabling them to display more colors, improve the vividness of the picture, and get closer to the colors of the real world as seen by the human eye.

About color, interested partners can understand some basic knowledge, such as color space, color gamut and color gamut standards, so that you can more easily understand the use of quantum dots.

The colorful horseshoe-like pattern as shown here is the CIE 1931 xy chromaticity chart, which you can simply understand as all the colors that the human eye can see.

For technical reasons, whether it is an LCD screen or an OLED screen, the number of colors they can display is limited. For example, for an ordinary LCD TV screen, the color gamut range is 100% BT.709, which is all the colors contained in the black triangle in the left one in the picture below.

Note: Although the color gamut range of DCI-P3 is larger than the BT.709 color gamut, DCI-P3 does not fully contain BT.709, nor can it be directly converted to a value.

If you want to improve the color gamut of LCD TVs, so that the screen can display more colors, we need to use the “wide color gamut” technology on the TV, and wide color gamut technology has two solutions, one is phosphor wide color gamut, one is quantum dot wide color gamut. Generally speaking, quantum dot material is better than phosphor material, the cost is also higher.

In order to facilitate consumer understanding, but also for the marketing effect, wide color gamut TV will generally use more than 100% BT.709 color gamut to quantify the color more this thing, although not rigorous, but for the average consumer can understand a roughly on. Phosphor wide color gamut TV can generally reach 120% to 130% BT.709 (color gamut volume), quantum dot wide color gamut TV can reach up to 157% BT.709 (color gamut volume). The general color gamut of OLED TVs is lower than that of quantum dot TVs.

So what exactly is quantum dot material? How does it work?
Simply put, the nanoparticles of certain substances will be excited when irradiated by blue light, and then emit specific wavelengths of light, such as cadmium sulfide, cadmium selenide, cadmium telluride can be, but on balance, cadmium selenide has the best stability and reliability, and is widely used in quantum dot TVs. Later, in order to legal and regulatory considerations, and the development of indium phosphide, a new cadmium-free quantum dot material.

The larger the particle size, the longer the wavelength of light emitted (toward the red end), and the smaller the particle size, the shorter the wavelength of light emitted (toward the purple end).

Based on this property, two different particle sizes (red and green) of cadmium selenide particles, mixed in organic solvent and then evenly applied to the substrate, can emit very high purity red, green and blue light (from the blue backlight) when illuminated by the blue backlight on the TV

Quantum dot film (light yellow)

Note that quantum dot materials need blue light irradiation to be excited, you can see the picture below, are irradiated by blue LED to show different colors, applied to the display is also the same to use blue LED, such as LCD TV and QD-OLED TV are so.

At present, quantum dot wide color gamut in the smart TV is still widely used, there are several brands in the country has a corresponding product, such as TCL / Thunderbird, Hisense, Xiaomi, Huawei wisdom screen, OPPO smart TV, Samsung also used more, Sony (Terry Phantom color) used in previous years, but now are changed to phosphor.

Misconceptions and rumors related to quantum dots
Misconception 1: QLED (quantum dot) TV is similar to OLED TV.

“QLED (quantum dot) TV is similar to OLED TV” this understanding is completely wrong, OLED TV is a new screen technology, pixel self-luminous, has a very high contrast ratio, and the current “QLED TV” is essentially an LCD TV, although OLED TV has certain shortcomings, such as burning screen problems, the overall picture brightness is not as high end LCD TV, but overall better than the LCD TV picture, but the price is also more expensive.

Misconception two: quantum dot TV is toxic and radioactive can not buy.

In fact, this misunderstanding, are the brand side of the mutual attack and smear, I do not have quantum dot products, I will black you, that your products are toxic, so you can not sell, the official can not pull the face, are let offline shopping guide in the “education” consumers, few brands personally down, of course, there are, such as Sharp is doing this.

Sharp a TV poster content
About the toxicity of quantum dot materials.

At the beginning of the quantum dot material with cadmium selenide, cadmium is indeed toxic to living organisms, but must be eaten to enter the body to reflect the toxicity, and the fact that the quantum dot film is closed inside the TV, not only that, cadmium selenide and indium phosphide both materials are not resistant to water and oxygen, so the surface of the quantum dot film and barrier film to prevent direct contact between quantum dot material and air, so even if the TV is disassembled and hand-held quantum dot film are fine, because accidentally eaten more impossible, and cadmium selenide, indium phosphide are not volatile, used in display equipment is actually very safe.

According to the EU in the directive on the restriction of the use of certain hazardous components in electrical and electronic equipment (RoHS) for the exclusion of cadmium provisions, the sale of televisions and monitors in Europe, the use of cadmium selenide quantum dots, used in display backlight applications, the limit for each square millimeter of the display is allowed to contain up to 0.2 micrograms of cadmium, to help you calculate, 65-inch TV is allowed to contain up to 0.23 Grams of cadmium, 55 inches allowed to contain up to 0.17 grams.

This limit is still mainly for environmental considerations, to prevent the quantum dot material from being discarded and pollute the soil and air, not because the use process is harmful to humans.

Indium phosphide is not currently restricted by RoHS, so new quantum dot material TVs have generally started to use indium phosphide as a new solution.

In fact, RoHS does not completely ban cadmium in display devices, as long as the content meets the exclusion clause, in the EU definition, as long as the content is less than 100PPM is equivalent to cadmium-free, so quantum dot material manufacturing companies have come up with a solution – red indium phosphide + green cadmium selenide, which can greatly reduce the cadmium content in the material, so that it meets the EU RoHS standard definition and is approved for sale on the market.

Although the product performance of cadmium selenide is superior to indium phosphide, but due to legal and regulatory restrictions, it may be that indium phosphide is the mainstream quantum dot material in the future.

Regarding the radioactivity of quantum dot materials.

Radioactivity refers to the indium phosphide in the indium element, there is a trace of radioactivity, since it is said that the trace, meaning that the dose is too low for the human body is actually no harm, Sharp’s move is actually very damaging, and strictly speaking is [a thief cries out for help], because the glass substrate of the LCD screen, will use a kind of ITO target (indium tin oxide target), this material can conduct electricity and high transparency, drive the upper and lower electrodes of the liquid crystal are using this material, so whether it is a cell phone / monitor / TV, as long as the LCD screen, will be used to contain indium targets, including Sharp’s own LCD TV.

In fact, even OLED screens also use ITO targets, so it can be said that even if there is no quantum dot material, indium elements are all around us.

So the level of Sharp’s smear is very low, even to their own heads.


Future applications of quantum dot materials.
① Quantum dots and OLED combination – QD-OLED screen

Meaning the addition of quantum dot material OLED TV, as mentioned earlier, OLED TV, although the color gamut is wide, but not as wide as quantum dot LCD TV, so you can do a combination in this regard, the quantum dot material into the OLED TV, so that OLED TV to get a wider color gamut, of course, now OLED TV are white LED, the use of quantum dot material, if you want to replace it with blue LED, and since the essence is still OLED, so still can not avoid the aging burn screen problem.

②Quantum dot and Micro-LED combination

Some people may have heard of Micro-LED technology, this technology can be achieved than OLED lower power consumption, higher screen brightness, higher contrast, better color performance, and will not be like OLED TV burning screen problems, but due to the process is difficult, currently can only do more than 100 inches of products, the price is even higher. The combination of quantum dot material and Micro-LED, the same can get a higher color gamut range better color performance, future technology maturity, cost reduction, almost certainly can replace the LCD TV and OLED TV, become the new darling of the display field.


To sum up.
Quantum dot and QLED refers to the LCD TV using quantum dot material to achieve a wide color gamut technology, can bring a richer and more vivid colors for LCD TV, the current application is also relatively wide, there are more products on the market, its safety is also no problem, you can rest assured that the purchase and use, the future of the new QD-OLED and Micro-LED and other new screen technology will also continue to use quantum dot material.

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