What is a Quantum Dot TV (aka QLED)?

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Despite some shortcomings, LCD TVs are the dominant type of TV sold and purchased by consumers. The acceptance of LCD TV has accelerated the disappearance of CRT and rear-projection TVs and is also the main reason why plasma TVs are no longer with us.

In recent years, OLED TV, led by LG, has been publicized by many for its "improved" performance as a successor to LCD. However, although it represents a step forward in TV technology, LCD TVs can still take a step forward with the incorporation of Quantum Dots

(aka QLED).

Quantum Dots and QLED refer to the same technology. QLED is a marketing term that Samsung and TCL use in the brand of their Quantum Dot TVs, which combine LED backlighting with Quantum Dots for color enhancement.

What is a quantum dot?

For the purpose of application in TV and video displays, a Quantum Dot is an artificial nanocrystal with semiconductor properties that can be used to improve the brightness and color performance displayed in still images and video on an LCD screen.

The Quantum Dots are emissive particles (a bit like phosphors on a plasma TV), but, in this case, when they are hit with photons by an external light source (in the case of the LCD TV application a blue LED light), each point emits color of a specific bandwidth, determined by its size. The larger points emit a light tilted towards the red and, as the points become smaller, they emit light more inclined towards the green.

When the quantum dots of designated size are grouped together in a structure (we will discuss this later in the next section) and combined with a blue LED light source, they can emit light through the entire color bandwidth required for TV viewing...

Taking advantage of the properties of Quantum Dot, TV manufacturers can improve the brightness and color performance of LCD TVs compared to current capabilities.

How quantum dots can be used in LCD televisions

Once the Quantum Dots have been created, the points of different sizes can be positioned randomly or in an organized way in a casing that can be placed inside an LCD TV (with an LCD TV the points are generally of two dimensions, one optimized for Green the other optimized for red).

  • Positioned inside a casing (called Edge Optic) along the edges of the LCD panel between a blue LED light source and the LCD panel (for LED / LCD TV with an illuminated edge).
  • On a "film improvement layer" positioned between a blue LED light source and the LCD panel (for Full Array TV or direct light LED / LCD).
  • On a chip positioned above blue LED light sources along the edge of an LCD panel (for LED / LCD TVs illuminated by the edge).

However, a blue LED sends light through the Quantum Dots, which are then excited to emit red and green light (which is also combined with blue from the LED light source).

The different colored light then passes through the LCD chips, the colored filters and on the screen to display the images. The added Quantum Dot emission level allows the LCD TV to display a more saturated and wider range of colors than LCD TVs without the added Quantum Dot level.

The effect of adding quantum dots to LCD televisions

TVs and video technologies cannot display the full-color spectrum. With this in mind, the triangles present within that spectrum show how much the various color technologies used in video display devices approach this goal.

As you can see from the reference triangles, LCD TVs that use traditional white LED backlighting or edge lighting show far less than the NTSC color standard adopted in 1953 for color transmission.

However, as you also see, when quantum dots are added to the mix, the color on an LCD TV has the ability to extend far enough to meet the standard NTSC color requirements.

The practical effect: the colors are more saturated and natural. Quantum Dots can also be used to meet the requirements of both HD (rec.709) and Ultra HD (rec.2020 / BT.2020) color standards.

LCD vs OLED

As mentioned in the introduction to this article, LCD TVs are the most common type used by families around the world.

However, LCD TVs have disadvantages in color saturation and black level performance, especially when compared to plasma TVs. The incorporation of black and white LED lighting systems helped in some way, but it was not enough.

In response to these shortcomings, the television industry (mainly LG) has pursued OLED as a solution, since televisions that incorporate OLED technology can produce both a wider color range and an absolute black.

Although the OLED is accepted as a better alternative to LED / LCD, after years of promises and failed attempts to reach the market, in 2014 only LG and Samsung entered the television market with large-screen OLED TVs that were introduced at CES 2013 using two different approaches.

LG uses a system called WRGB, which is a combination of white-light OLED subpixels and color filters to produce images, while Samsung has incorporated red, green and blue light-emitting OLED subpixels.

Samsung abandoned the production of consumer OLED TVs in 2015, leaving LG and, and Sony, the only OLED TV sources destined for the US consumer market.

OLED TVs look really cool, but there's a big problem that keeps the rest of the TV industry from bringing OLED TVs to the market on a large scale, the costs.

Despite the claim that LCD TVs are more complicated in the structure than OLED TVs, the real fact is that OLEDs are more expensive to produce in the large screen sizes required for televisions.

This is due to defects that occur in the production process and that cause a large percentage of OLED screens rejected by the use of large screens. As a result, most of the alleged advantages of OLEDs (such as the ability to display a wider color gamut and a deeper black level) than LED / LCD TVs are suffocated.

Taking advantage of OLED production problems and the ability to incorporate Quantum Dots into the currently performed LED / LCD TV design (and very few modifications required in the assembly line), Quantum Dots could be the ticket to bring the performance of the LED / LCD TV closer to that of what TV producers were hoping for with OLED - and at much lower costs.

LCD with Quantum Dots vs. OLED

Without going into many technical details, when comparing all four sets, it turns out that the color coverage of the two Sony Quantum Dot LED / LCD sets used for comparison and the original Samsung OLED set are very close, while LG OLED set actually it seems to work badly.

On the other hand, while the Samsung set is capable of producing high brightness, both Sony Quantum Dot LED / LCD and LG OLED sets are very close.

However, the most significant difference is in energy consumption. OLED TVs consume more power than both Sony sets used in this comparison, especially considering that the Sony 65-inch 4K set consumes less energy than both 55-inch OLED TVs. This would mean, except for any engineering progress of future generations of OLED TVs, that a 65-inch OLED TV could consume more power than its equivalent quantum dot-enabled LED / LCD TV.

While LED / LCD TVs consume energy at a more stable level regardless of the brightness output (although other TV functions, such as Smart TVs, etc., when engaged can affect energy consumption), the energy consumption of the TV OLED changes with the brightness level required to produce images. So the brighter the content, the more energy is consumed and, of course, the involvement of Smart TV and other features will also change this.

Thus, the additional cost factor in both the production and purchase of an OLED TV may not offer a great improvement over a LED / LCD TV with Quantum Dot.

Quantum Dots: a colorful present and future

The main suppliers of Quantum Dot technology for use on TV are Nanosys and 3M, which provide the Quantum Dot film option (QDEF) for use with full matrix backlit LED / LCD TVs.

The use of Quantum Dots has made a great leap forward as several TV producers have put on display Quantum Dot-enabled televisions at fairs such as Samsung, TCL, Hisense / Sharp, Vizio, and Philips. Of these, Samsung and Vizio have launched models on the market in the United States: Samsung makes their Quantum Dot TVs as QLED TVs, while Vizio uses the term Quantum

.

Strangely, LG, which showed some prototypes of Quantum Dot TV in 2015, apparently decided to retire and put more resources into its Nano Cell technology on selected LCD TVs and to make more expensive TVs using OLED technology.

Since LG and Sony (since 2019) are the only producers of OLED TVs (Sony OLED TVs use LG OLED panels) for the US market, the Quantum Dot alternative to the color enhancement offered by Nanosys and 3M could allow LCDs to continue to dominate the market for years and decades to come.

Next time you go to buy a TV, check if it has the "Color IQ", "QLED" "QD", "QDT", "Quantum" or a similar label on the set or in the user manual - which says... the TV uses Quantum Dot technology.

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