Quantum dots glow a specific color when they are hit with any kind of light. Here, a vial of green quantum dots are activated by a blue LED backlight system.
If you look at the CES 2015 word cloud—a neon blob of buzz radiating from the Nevada desert, visible from space—much of it is a retweet of last year’s list. Wearables. 4K. The Internet of Things, still unbowed by its stupid name. Connected cars. HDR. Curved everything. It’s the same-old, same-old, huddled together for their annual #usie at the butt-end of a selfie stick.
But there at the margin, ready to photobomb the shot, is the new kid: quantum dot. It goes by other names, too, which is confusing, and we’ll get to that in a minute. Regardless of what you call it, QD was all over CES this year, rubbing shoulders with the 4K crowd. You may have heard people say it’s all hype. Those people can go pound sand. Quantum dot is gonna be the next big thing in TVs, bringing better image quality to cheaper sets.
A Quantum-Dot TV Is an LCD TV
The first thing to know is quantum-dot televisions are a new type of LED-backlit LCD TV. The image is created just like it is on an LCD screen, but quantum-dot technology enhances the color.
On an LCD TV, you have a backlight system, which is a bank of LEDs mounted at the edge of the screen or immediately behind it. That light is diffused, directed by a light-guide plate and beamed through a polarized filter. The photons then hit a layer of liquid crystals that either block the light or allow it to pass through a second polarized filter.
Before it gets to that second polarizer, light passes through a layer of red, blue, and green (and sometimes yellow) color filters. These are the subpixels. Electrical charges applied to the subpixels moderate the blend of colored light visible on the other side. This light cocktail creates the color value of each pixel on the screen.
With a quantum-dot set, there are no major changes to that process. The same pros and cons cited for LCD TVs also apply. You can have full-array backlit quantum-dot sets with local-dimming technology (Translation: good for image uniformity and deeper blacks). There can be edge-lit quantum-dot sets with no local dimming (Translation: thinner, but you may see light banding and grayer blacks). You can have 1080p quantum-dot sets, but you’re more likely to see only 4K quantum-dot sets because of the industry’s big push toward UltraHD/4K resolution.
But a Quantum-Dot TV Is Different
In a quantum-dot set, the changes start with the color of the backlight. The LEDs in most LCD TVs emit white light, but those in quantum-dot televisions emit blue light. Both types actually use blue LEDs, but they’re coated with yellow phosphor in normal LCD televisions and therefore emit white light.
Here’s where the quantum dots come in. The blue LED light drives the blue hues of the picture, but red and green light is created by the quantum dots. The quantum dots are either arranged in a tube—a “quantum rail”—adjacent to the LEDs or in a sheet of film atop the light-guide plate.
Quantum dots have one job, and that is to emit one color. They excel at this. When a quantum dot is struck by light, it glows with a very specific color that can be finely tuned. When those blue LEDs shine on the quantum dots, the dots glow with the intensity of angry fireflies.
“Blue is an important part of the spectrum, and it’s the highest-energy portion—greater than red or green,” explains John Volkmann, chief marketing officer at QD Vision, which makes quantum dots for several TVs and monitors. “You start with high energy light and refract it to a lower energy state to create red or green… Starting with red or green would be pushing a rock uphill.”
Quantum dots are tiny, and their size determines their color. There are two sizes of dots in these TVs. The “big” ones glow red, and they have a diameter of about 50 atoms. The smaller ones, which glow green, have a diameter of about 30 atoms. There are billions of them in a quantum-dot TV.
If you observed quantum-dot light with a spectrometer, you would see a very sharp and narrow emission peak. Translation: Pure red and pure green light, which travels with the blue light through the polarizers, liquid crystals, and color filters.
Because that colored light is the good stuff, quantum dots have an advantage over traditional LCD TVs when it comes to vivid hues and color gamut. In a normal LCD, white light produced by the LEDs has a wider spectrum. It’s kind of dirty, with a lot of light falling in a color range unusable by the set’s color filters.
“A filter is a very lossy thing,” says Nanosys President and CEO Jason Hartlove. Nanosys makes film-based quantum-dot systems for several products. “When you purify the color using a color filter, then you will get practically no transmission through the filter. The purer the color you start with, the more relaxed the filter function can be. That translates directly to efficiency.”
So with a quantum-dot set, there is very little wasted light. You can get brighter, more-saturated, and more-accurate colors. The sets I saw in person at CES 2015 certainly looked punchier than your average LCD.
That Sounds Expensive
There’s no doubt that quantum-dot TVs will cost more than normal LCDs—especially because they’re likely to be 4K sets. But quantum-dot is getting a lot of buzz because its cheaper than OLED.
In most peoples’ eyes, OLED TVs are the best tech available. But they’re expensive to build and expensive to buy—you’re looking at $3,500 to as much as $20,000—and the manufacturing process differs in several key ways. That’s a big reason LG is the only company putting big money into building them.
Conversely, quantum-dot sets don’t require overhauling the LCD fabrication process, and they produce a much wider color gamut than traditional LCDs. They’re closer to OLED in color performance, and they also can get brighter. That’s important for HDR video.
“The attraction to the OEM is that this is a pure drop-in solution,” says Nanoco CEO Michael Edelman, whose company makes quantum-dot film in a licensing deal with Dow Chemical. “They remove a diffuser sheet in front of the light-guide plate and replace it with quantum-dot film. Nothing in the supply chain gets changed, nothing in the factory gets changed. They get, in some cases, better than OLED-type color at a fraction of the cost.”
As you’d expect, companies making film-based and tube-based solutions are touting each approach as superior. QD Vision claims its tube-based approach is easier and cheaper to implement, and it can boost the color performance of cheaper edge-lit LCD sets. According to QD Vision, the oxygen-barrier film needed for film-based dots is costly, which explains why Nanoco and Nanosys are partnering with Dow and 3M for that film.
Film-based suppliers say their method has the upper hand due to “light coupling,” or the ability to feed all that quantum-dot light directly into a light-guide plate. The film layer also purportedly works better with full-array backlight systems, which will be used in a lot of UHD and HDR TVs.
Super! So This Is OLED for Less Money?
Not entirely. Color gamut is important, but it’s only one aspect of picture quality. Because these are LCD sets, they won’t have the blackest blacks, super-wide viewing angles, and amazing contrast of OLED. And while the extra brightness and saturation makes onscreen colors really pop, all that luminance may create light bleeding.
Some quantum dots also contain cadmium, which is toxic at high levels—think “factory emission” levels rather than “sealed tube or film in your TV” levels. Still, there are health and environmental concerns, especially if a bunch of quantum-dot TVs end up in landfills. The European Union restricts the use of cadmium in household appliances. Some quantum-dot producers are marketing their product as cadmium-free. QD Vision, which supplies quantum dots for TCL’s new flagship 4K TV, Sony’s well-reviewed 2013 Triluminos sets, and Philips and AOC monitors, still uses cadmium.
“There are only a couple of materials that deliver on the promise of quantum dots,” says QD Vision’s Volkmann. “The other is based on indium. Cadmium is superior with respect to delivering higher-quality color, meaning a broader color gamut. But also much more energy-efficient at converting blue light to other forms of light that allow you to fill out that spectrum. The folks making indium-based solutions like to paint cadmium as the bad guy… Cadmium is under observation by different regulatory agencies around the world, but it turns out indium is too.”
Nanosys, which produces both cadmium and cadmium-free quantum dots, agrees that cadmium-based dots are more efficient.
“Cadmium-based materials have a narrower spectral width,” says Nanosys’s Hartlove. “More pure color. And what that means is the other things the system has to do in order to keep that color pure, the burden on the rest of the system is reduced.”
Hartlove also says that cadmium may be a greener solution. The cad selenide crystal used in quantum dots isn’t as toxic as pure metallic cadmium, and the efficiency of their color-producing ways has benefits.
“The type of power we generate in the US from coal-based power plants throws cadmium into the atmosphere,” says Hartlove. “That’s one of the byproducts of burning coal. And you look at the net cadmium content over this whole lifecycle, and it turns out that cadmium sequestration is actually net better for the environment.”
Why Isn’t Everybody Calling It “Quantum Dot”?
Each manufacturer with a quantum-dot TV set seemingly has a different name for the technology. Samsung likes “nano-crystal semiconductors.” Sony has new Triluminos TVs that “incorporate the same benefits as quantum dots.” LG, TCL, Hisense, and Changhong are actually calling it quantum dot, which is nice.
“The term quantum dot is generic,” says Hartlove. “Each company kind of wants to grab this for their own and brand it their own way. That will probably lead to some consumer confusion… but I think most of the industry will converge on a way to describe this technology.”
There are slight differences between the technologies everyone’s using, but they’re variations on a theme. The differences center on whether the TVs are edge-lit or back-lit with quantum dots, and whether the systems use cadmium- or indium-based quantum dots.
Who Is Making Quantum Dots?
At this stage, three companies are the big players in the quantum-dot TV landscape.
QD Vision specializes in glass-tube “edge-lit” components, and its systems will be found in TCL TVs and monitors from Philips and AOC. It supplied the quantum-dot component for Sony’s 2013 Triluminos sets, but Sony recently ditched the company in favor of another.
Nanoco focuses on cadmium-free, film-based quantum dot systems. They have a licensing deal with Dow Chemical, and Dow is currently building a factory in South Korea to ramp up production of quantum-dot film. Nanoco’s cadmium-free technology will be found in LG’s quantum-dot TVs in 2015.
Nanosys is another film-based producer that has partnered with 3M on the film-sheet tech. It makes both cadmium-based and cadmium-free quantum dots. They are the company behind Amazon’s HDX 7 display and the Asus Zenbook NX500, and Samsung licenses the cadmium-free quantum-dot tech in its new SUHD 4K sets from Nanosys. Nanosys is also working with Panasonic, Hisense, TCL, Changhong, and Skyworth on future TVs.
When Can I Get One, and What Will It Cost?
The new TVs showcased at CES each year usually start hitting stores in the spring, but some higher-end models don’t arrive until the fall. That’s a little bit of a wait, but it’s probably for the best—there are UltraHD content-delivery complications to work out, anyway.
The TV we know the most about in terms of pricing is TCL’s 55-inch H9700, and we still don’t know much. It’s already available in China for around $2,000 U.S., and TCL representatives at CES hinted that it will be close to that mark when it hits the U.S.
Expect that to be at the low end of the quantum-dot price bracket; LG, Samsung, and Sony generally have pricy TVs, and similar 4K LCDs from last year—minus the quantum dots—went in the $2,000 to $3,000 range for a 55-incher. For this initial wave of quantum-dot TVs, most MSRPs will probably fall between $2,500 to $4,000 for a 55-inch 4K set.