Quantum-dot solution promises more colorful, energy-efficient LCD TVs

Quantum-dot solution promises more colorful, energy-efficient LCD TVs

Technology News |
By eeNews Europe

Quantum dots are light-emitting semiconductor nanocrystals that can be tuned — by changing their size, nanometer by nanometer — to emit all colors across the visible spectrum.

QD Vision has developed an optical component that can boost the color gamut for LCD televisions by roughly 50 percent, and increase energy-efficiency by around 20 percent.

In June 2014, Sony used QD Vision’s product, called Color IQ, in millions of its Bravia ‘Triluminos’ televisions, marking the first-ever commercial quantum-dot display. In September 2014, Chinese electronics manufacturer TCL began implementing Color IQ into certain models.

These are currently only available in China, “because a lot of growth for the TV market is there,” explained Seth Coe-Sullivan PhD ’05, co-founder and chief technology officer of QD Vision, who co-invented the technology at MIT. But within a couple of months, Coe-Sullivan said, these displays will be “rolling out to the rest of the world.”

In conventional LCD TVs, pixels are illuminated by a white LED backlight that passes through blue, red, and green filters to produce the colors on the screen.

Phosphors are required to convert a blue light to white; because of this process, much light is lost, and displays only reach about 70 to 80 percent of the color gamut. Manufacturers can potentially boost color by incorporating more LEDs, but this costs more and requires more energy to run.

Color IQ is a thin glass tube, filled with quantum dots tuned to red and green, that is implemented during the synthesis process. Manufacturers use a blue LED in the backlight, but without the need for conversion phosphors. As blue light passes through the Color IQ tube, some light shines through as pure blue light, while some is absorbed and re-emitted by the dots as pure red and pure green.

With more light shining through the pixels, LCD TVs equipped with Color IQ produce 100 percent of the color gamut, with greater power efficiency than any other technology.  

“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,” said QD Vision co-founder and scientific advisor Vladimir Bulovic, the Fariborz Maseeh Chair in Emerging Technology at MIT, who also co-leads the MIT Innovation Initiative.

While developing its Color IQ — which replaces phosphor in displays — the company developed a much greener synthesis which involves replacing alkyl phosphine solvents with long-chain hydrocarbons, which are less hazardous, and replacing cadmium and zinc building blocks with less hazardous materials.

“We’ve been able to show, cradle to grave, from the materials we use to how we make it to how it is put to rest, that there’s an environmental benefit,” Coe-Sullivan explained.

Other technologies, called organic light-emitting diode (OLED) displays, use an organic compound to reach upward of 100 percent of the color gamut — but they are expensive to produce. LCD TVs made with Color IQ are as colorful, but are made for a few hundred dollars less and operate with greater efficiency, claimed Coe-Sullivan.

QD Vision’s technology began at MIT more than a decade ago. Coe-Sullivan, then a PhD student in electrical engineering and computer science, was working with Bulovic and students of Moungi Bawendi, the Lester Wolfe Professor in Chemistry, on implementing quantum dots into electronic devices.

In 2010, the company launched its first product, a QD light bulb, with partner Nexxus Lighting. However, realizing this $100 light bulb would soon need to sell for $10 to remain competitive, QD Vision saw that it needed a new market: quantum-dot displays. “Making a transition like that [from lighting to displays] tests the nerves of folks involved, from top to bottom,” Coe-Sullivan says. “QD Vision’s story is one of many … tense moments, and that was one of them.”

Pooling all resources into displays, the company eventually caught the eye of Sony, and in 2013 became the first to market with a quantum-dot display. Today, QD Vision remains one of only two quantum-dot display companies that have seen their products go to market.  

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