A leading light

By | Science & Technology
Quantum Dots being produced at PlasmaChem at a kg scale. Credit@Antipoff

Korean electronics giant LG recently unveiled its new televisions at the Consumer Electronics Show (CES) in Las Vegas. The international event is well known as the space where innovators in TV technology launch their new product lines. At the event, LG announced its new range of 4K ultra-high definition television displays (UHDTVs). The displays use quantum dot technology to produce more vivid colour images than ever. It is anticipated that 2015 may see quantum dot technology enter the mainstream and overtake current LED and LCD rivals.

A quantum dot (QD) is a nanocrystal made of semiconductor materials, in this case made from the inorganic compound cadmium selenide. They are small enough that they exhibit quantum mechanical properties and their size determines their colour. Billions of these QDs fit into a single TV. The LEDs in most LCD TVs emit white light; quantum dot televisions emit blue light. In QD TVs, blue hues are driven by the blue LED backlight. Reds and greens are produced by the quantum dots. They may be arranged in a tube or as a “quantum rail”, either next to the LED or as a film lying atop the screen’s backlight. As the light of the LED strikes a QD, it emits a very specific colour.

The chief marketing officer at QD Vision, John Volkmann, explains, “Blue is an important part of the spectrum, and it’s the highest-energy portion – greater than red or green…You start with high energy light and refract it to a reduced energy state to create red or green…Starting with red or green would be pushing a rock uphill.”

The QDs in LG’s latest UHDTVs come in two sizes: the ‘big’ ones are 50 atoms wide and glow an intense red, the ‘small’ ones are 30 atoms wide and glow green. The smaller the QD, the more blue it appears. When the light emissions are viewed using a spectrometer, two distinct and narrow peaks are observed representing the intense purity of the light emitted by the QDs. Other colours are achieved as the red and green light travels with the blue through liquid crystals, polarisers and colour filters.

Blue LEDs offer a significant advantage in terms of vivid hues and vibrant colours. This is because the white LEDs typically used in LCD TVs encompass a wider spectrum producing a lot of ‘extra’ light, which becomes wasted. As President and CEO of Nanosys Jason Hartlove explains, “A filter is a very lossy thing…When you purify the color using a color filter, then you will get reduced transmission through the filter. The purer the color you start with, the more relaxed the filter function can be. That translates directly to efficiency.” Simply, the advantage of QD technology is a brighter, punchier, more accurate and more saturated display.

The technology showcased at CES is typically available within twelve months so consumers may expect to see QD technology in stores by autumn or even springtime. This technology is a timely arrival. While film producers and broadcasters have known how to produce ultra-high definition images for some time now, consumer technology has as yet been unable to display it to this standard. QD technology aims to match these quality demands and display the intensely beautiful colours producers intended.

Quantum dots have been around for a while, even though their potential in consumer electronics is just being realised. They also have multiple applications in biology. For example, QDs are used for highly sensitive cellular imaging as well as tracking the movement of molecules through cells in real time. QD technology is even being used in gene silencing to help deliver molecules into cells.

How might recent discoveries in physics, such as the Higgs Boson, influence consumer electronics in 10 or 20 years?

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