The Ultimate Game Changers

In an art gallery, the lighting in which a piece of art is shown is incredibly important to the viewer’s experience. Dial up the light provided by a spotlight overhead, and the reds in the canvas start to pop out a little more. The dark blacks start to clearly define themselves against the lighter colors in the background, and the outlines become clearer. With this simple change, one can significantly alter the viewer’s visual experience. In a similar fashion, the television industry has largely improved image quality by altering the backlight that provides a television with its source of light. And the secret weapon behind such a development is a tiny, tiny cluster of atoms, known as a quantum dot.

A quantum dot is a crystal 10,000 times smaller than a human hair. It consists of atoms that emit light at a very specific frequency when a current is run through it. It turns out that the size of the crystal determines the frequency emitted; that is, by changing the crystal’s size one gets different colours. Make the crystal smaller, and the emitted frequencies resemble blues and violets. Make it larger, and the resulting colours become oranges and reds. Any size in between matches up to a colour in the middle chunk of the spectrum.

Spectrum
The color of a quantum dot depends on the size of the crystal

These dots were discovered thirty-five years ago by a researcher named Alexy Ekimov, but the development of their potential for enhancing screen resolution just began in the early 2000s. Since then, two prominent companies, one named QD Vision and the other named Nanosys, have amassed a large share of the quantum dot market by either manufacturing the dots by millions or developing screens that implement them. And wisely have they done so. Quantum dots have rapidly infiltrated screen technology starting this year and have utterly transformed the quality of screen resolution.

In a standard television, an image is projected on the screen by a white backlight undergoing a series of diffraction and filtering processes. At the very back of the television, white light is emitted by a row of LED lightbulbs. These bulbs emit blue light, but they are covered in a layer of yellow phosphorus so that the resulting light is white. After emission, this light enters the layers of filters that build the desired image. It is before the white light actually goes through any filters that the quantum dots intervene.

Quantum dots enhance image quality by emitting a white backlight that is purer than the one provided by the standard setup of the phosphorus-covered LEDs. They do so by emitting two colours — red and green — that, when combined with blue light, make what is called a trichromatic white light. A trichromatic white light is one made up of blue, green and red frequencies combined, and its frequency is much closer to the precise value that defines the colour “white” than non-trichromatic white light. Thus, the light ends up being a purer white than a white that consists of a wide range of colour shades. Also, by virtue of the on-target color emission of the quantum dots – one can meticulously design them so that they emit exactly a red or exactly a green – the emitted light ends up being that much more precise.

As for the setup that allows for such an intervention by the quantum dots, the row of LEDs need no longer to be covered by the layer of yellow phosphorus. Rather, they are left to emit blue light. When this light strikes the layer of quantum dots, the dots, depending on their size, emit either red or green light. These two vibrant emitted colours travel along with the remnant light of the LEDs to produce the trichromatic white. With such a white light, the filters along the path perform their function more efficiently, since they do not need to “chop down”* the trichromatic white light as much. Also, the brightness of images significantly improves since the backlight is able to make its way to the screen with greater intensity left after filtering.

With quantum dot technology, the color gamut of the screen – a value that indicates the range of colors a screen can reproduce – is significantly improved: Increases range from 40% to 50%. With such a jump, viewers will view color frequencies they have never before seen on their televisions.

With such a jump, viewers will view color frequencies they have never before seen on their televisions.

Such an enhancement in quality, oddly enough, is also more convenient for energy usage. By removing the phosphorus layer that dimmed the light emitted by the LED bulbs, a larger percentage of the energy required to power those bulbs is actually reaching the screen. Energy efficiency is estimated to improve by 20%.

Given all of these improvements, quantum dots have been quickly incorporated into television screens. Just this year, Quarterly TV Design and Features estimates that over 1.3 million quantum dot televisions will be shipped. By 2025, it is estimated that 60% of televisions will have quantum dots in them and that 51% of monitors will use quantum dots.

LightBulbvA1

Although quantum dots have the potential for use in the backlight emission stage of the television and into the screen itself, its developers are proud that such an improvement in screen resolution results just from adding a layer of material to the television: One does not need to tinker with the complex diffraction and filtering past the row of LEDs. QD Vision’s co-founder and MIT scientist Seth Coe-Sullivan stated the function of quantum dots quite clearly when he compared the dots to a lightbulb: “The value proposition is that you are not changing the display, all you’re doing is replacing the light bulb, and yet the entire display looks much better. The colors are much more vivid — known as much more saturated — allowing you to generate a much more believable image.” Quantum dots — a marvelous optics phenomenon, a screen resolution game changer, and a smart change from a lightbulb.

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Sources:

*term used by Seth Coe-Sullivan in an interview with Kate Greene.

http://www.kategreene.net/how-quantum-dots-will-improve-lcds/

http://phys.org/news/2014­11­quantum­dot­technology­lcd­tvs­energy­efficient.html

https://www.youtube.com/watch?v=GFUO6MxC4rg

https://faculty.washington.edu/jpalmer/files/Teller/ByChapter/tellerChapter07.pdf

http://spectrum.ieee.org/tech­talk/consumer­electronics/audiovideo/what­the­heck­are­quantum-dots

http://www.cnet.com/news/led­lcd­backlights­explained/

http://www.wired.com/2015/01/primer­quantum­dot/

http://whatis.techtarget.com/definition/quantum­dot

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