What the Heck Are Quantum Dots?

And why will they be the hottest TV tech at CES?

4 min read

What the Heck Are Quantum Dots?
Photo-illustration: Getty Images

It wouldn’t be CES without an attempt to launch the next big thing in TV technology. The next big thing was recently supposed to be OLED TVs. That didn’t work out so well; OLED manufacturing costs haven’t come down as fast as anticipated; yields are still low for large-screen OLEDs and prices are staying high.

The next big thing for 2015, we’ll likely be told at CES, will be the quantum dot TV. Sounds pretty space-agey, for sure. But before you rush to throw out the 3D-4K-LED TV you bought last year, the one you thought was the apex of display technology (or before you ignore the news as just another lame attempt by TV manufacturers to get your attention) let’s demystify this latest “breakthrough.”

First, what quantum dot television technology is not. It is not a new way of creating a television picture on a screen. Rather, the technology that’s translating the broadcast signal to an image is the same old liquid crystal display (LCD) technology that has been around for more than a decade, and in the past couple of years vanquished the competing technology, plasma TVs.

Wait, you say, I don’t have an LCD TV, I have an LED TV. At least that’s what the box said.

Sorry to disappoint, but your LED TV is an LCD TV. The LED refers to the backlight; the original LCD TVs were backlit by fluorescent tubes; switching to LEDs for backlighting let manufacturers make TVs thinner and more efficient.

Quantum dot technology promises to be an even better backlight than LED.

Here’s why. A TV picture is made up of pixels (picture elements), each with red, green, and blue subpixels. In an LCD TV and most LED TVs, the LCD display creates those colors by filtering white light. (Typical LED TVs use white LEDs—actually blue LEDs coated in a yellow phosphor—on one or two edges of the TVs. What manufacturers call LCD TVs use fluorescent tubes behind the screen.) White light, however, doesn’t just contain the pure red, green, and blue that make up the TV image; it contains pinks, and yellows, and oranges and other extras that get through to slightly change the red, green, and blue tones.  And the better the filters are at blocking these extraneous colors, the less light makes it to your eye—not an efficient way to create a bright picture. Some LED TV manufacturers in the past addressed this problem by using red, green, and blue diodes instead of white ones; this, however, turned out to be too costly and too power-hungry an approach.

Quantum dots, which are light-emitting semiconductor nanocrystals that can absorb light of one wavelength and convert it efficiently to light of other very specific wavelengths, can create even more distinct reds, greens, and blues than colored LEDs, says Seth Coe-Sullivan, co-founder and CTO of QD Vision. QD Vision spun out of MIT a decade ago to commercialize quantum dot displays.  

QD’s technology starts with a blue LED (not a blue LED tweaked to be white). The system then routes light from the LED through a tube filled with red and green quantum dots. These fluoresce, generating red and green light. At the other end of the tube, the light that comes out looks white to the eye, but is actually a blend of the original pure blue, plus the pure red and pure green generated by the quantum dots. Because it is so pure, the vast majority of it passes through the LCD’s filters unobstructed, keeping its brightness. TV manufacturers using these little tubes as backlights place them at the edges of the displays.

QD Vision isn’t the only company that has been developing quantum dot backlighting. Nanosys, working with 3M, created Quantum Dot Enhancement Film (QDEF). In this approach, the blue LEDs again sit at the edges of the display and the layer of quantum dots covers the entire back of the LCD panel. Moving the dots away from the LEDs could mean that they’ll last longer, because they are less likely to be stressed by temperature changes. But this approach reportedly raises the cost of the backlight dramatically.

An approach further in the future is creating an entire TV display out of quantum dots, rather than just using them as a backlight. In fact, that was QD Vision’s original plan, according to Coe-Sullivan. “We founded the company thinking we were going to make an emissive display technology called QLED; we’d take the OLED device structure, but use quantum dots as the emissive layer. You’d get better color and better efficiency than OLEDs.”

But, he says, “the reliability is not there, though we’re still working on this approach in R&D.”

“It was far easier to improve LCD technology,” says Coe-Sullivan, than to launch an entirely new technology.

So actual QD displays aren’t coming anytime soon.

“We are a way off, if ever, before we see QDs being used for emissive displays, says Paul O’Donovan, a principle research analyst for Gartner.

This means that when you hear about “QD TV”, you should think “QD-backlit LCD TV”, because that’s what manufacturers will be sending to retailers for the foreseeable future.

It looks like we’ll be seeing both the QD Vision and the Nanosys/3M approaches at CES: 

  • Sony used QD Vision’s technology in more than a million TVs sold in 2013, and will likely be back at CES with new models.
  • TCL in December announced its first QD TV, a 55-inch 4K unit for the China market, also using QD Vision’s technology, and it plans to make an announcement at CES.
  • Shortly after the TCL news came out, LG announced that they were planning to announce (seriously) QD TVs at CES using quantum dot film—they didn’t name names, but that’s likely the Nanosys/3M technology.
  • Samsung hasn’t made an official announcement, but has made it clear that it will have QD news at CES.

Other companies are sure to jump on the QD bandwagon; it’s going to be the hot TV topic at CES, pushing any announcements of 4K/Ultra High Definition TV or future OLED models into its shadow.

Don’t entirely count out OLED for the long run, however. OLED TV still has advantages over any type of LCD TV—it needs no backlight, can refresh far more quickly, and can be made thinner, lighter, and more flexible. And it should eventually be cheaper to make, though yields aren’t there yet.

“LG has been managing to ship OLED TVs in some volumes,” O’Donovan says, “admittedly only to a few markets and at a relatively high cost.” And though Samsung has said it won’t be making any moves in the OLED TV area in 2015, its recent investment in OLED equipment maker Kateeva shows that it’s still betting on OLED for its future.

Update 6 January: TCL indeed unveiled a TV using QD Vision’s technology at CES; Samsung went with the Nanosys film technology; LG is reportedly planning to use quantum dot film technology from Nanoco.

The Conversation (0)