By Russ Banham
By Russ Banham
Since the dawn of high definition, electronics companies have raced to make ever larger TVs at lower prices while making colors more lifelike and brilliant.
And while consumers have come to expect incremental improvements year after year, the quest to create a TV that can produce all of the colors that the naked eye sees has reached a remarkable turning point.
After a generation of scientific discovery and technical experimentation, a new era of television may be upon us in the form of quantum dot technology.
So small are these dots that they cannot be seen with either the naked eye or a typical microscope. Yet it’s their very stature that makes them able to convert light into any color in the visible spectrum.
Quantum Dots Discovered
Renowned chemical physicist Louis Brus discovered quantum dots at Bell Labs in the 1980s, and it took decades to transform his groundbreaking discovery into commercial products. Much of that work was done at Nanosys, a nanotechnology company co-founded not by Brus, but by one of his graduate students, Paul Alivisatos.
Although the quantum dot technology developed by Nanosys is inextricably linked to 4K displays today, the underlying technology was originally developed for a different application.
“We were investigating the creation of really high-quality semiconductor crystals for use in telecommunications,” Alivisatos said. “We wanted these materials to be very precisely controlled in terms of the number of atoms. It was a fascinating journey, particularly since many people didn’t think what we were hoping to achieve was possible.”
In the 1980s and ’90s, the hypothesis was that making small semiconductor crystals was more prone to defects than making larger ones. It turned out that the opposite was true.
“My research group measured the melting temperature in making the crystals, and as it became lower and lower, it resulted in fewer defects,” said Alivisatos, Samsung professor of chemistry and materials science at the University of California, Berkeley, where he is also vice chancellor for research.
Alivisatos and other researchers eventually determined the reason: Smaller crystals take less time to heat and cool. This reduces the likelihood of contamination and, consequently, defects. The same phenomenon is at play when the Earth’s mantle makes diamonds, explaining why the tinier a diamond, the less chance of faults.
Every Color We Can See
A related discovery involved the quantum effect — the idea that when a crystal becomes very small, it affects the energy levels of electrons inside. In lighting applications, this means higher frequencies of light are emitted as the size of the crystal decreases. A range of different-sized crystals produces a rainbow of colors.
Quantum dots are composed of three parts: core, ligand and shell. The size of the core determines what color a quantum dot emits, and the shell protects the core from exposure to air and moisture.
“The size and the shape of the dots determine their electronic characteristics,” Alivisatos said. “When you change the number of atoms in a crystal, you can change the color at will.”
In other words, by changing the size of a quantum dot, you can control the color of light that it emits. This is similar in effect to the different sounds produced by a guitar string. The shorter the guitar string, the higher the pitch. The longer the string, the lower the pitch. Quantum dots behave in much the same way. But rather than being tuned to emit sound of different pitches, quantum dots are tuned to emit light of different colors. Bigger dots emit longer wavelengths such as red; smaller dots emit shorter wavelengths such as green.
Although red and green are great for Christmas, they’re not ideal for high-quality TVs. But here’s where the technology gets really interesting: The LEDs, or light-emitting diodes, that produce the backlight necessary to illuminate displays in televisions are blue.
And because blue, red and green are the primary colors of white light, a quantum dot can produce every color seen by the naked eye. As Alivisatos put it, “Quantum dots can make colors that match the sensors in our eyes.”
For his work in developing nanocrystals, Alivisatos was awarded the prestigious National Medal of Science for Chemistry in 2014.
What Took So Long?
Soon after the discovery of quantum dot technology, scientists began to look at how they could turn a laboratory curiosity into a commercially viable product. But that took a company dedicated to its commercialization.
The Samsung Advanced Institute of Technology, the company’s research and development hub, began to explore the potential of quantum dots in 2001.
That same year, Alivisatos and entrepreneur Larry Bock founded Nanosys with the express mission of commercializing the technology.
Nanosys in its early years achieved modest success at best. No products were developed through 2008, and a planned initial public offering failed to get off the ground.
Then Jason Hartlove took the reins of Nanosys as president and CEO. An electrical engineer with 20 patents to his credit, Hartlove had a track record of turning emerging technologies into successful products and emerging companies into successes. At Hewlett-Packard, Hartlove helped commercialize the first optical mouse. As president of the Imaging Solutions Division at MagnaChip Semiconductor, he transformed the internally focused semiconductor group into a multinational company.
Hartlove was optimistic about the future of quantum dots in television displays, envisioning them collectively as a more affordable alternative to competing technologies.
“LED backlight technology is nothing new, having first come to the market in 2004 with Sony’s Bravia TV,” said Hartlove. “That television used separate and distinct red, blue and green LED lights to create a broad spectrum of colors. Its performance was phenomenal.”
But red, blue and green LEDs were not cheap. And they produced a lot of heat, which had to be dissipated.
“The original Bravia 42-inch display unit cost well over $5,000 and was the size of a battleship to address the heat created by the LED,” Hartlove recalled.
To bring down the price point, TV manufacturers substituted white LEDs for the expensive red, blue and green variety. But white light contains a lot of blue and yellow colors and not much in the way of red and green, which diminished the color quality. The goals of a less expensive, more compact display unit were achieved, but at reduced color performance.
Quantum dots appear to solve this dilemma.
“When a quantum dot is hit with light, it responds with a very specific color that can be precisely controlled,” said Hartlove. “The ability to precisely convert and tune a spectrum of light made them ideal.”
Just Like The Movies
Once the technology was perfected, TV manufacturers lined up to incorporate quantum dots into their displays, which involves a unique process.
Making a quantum dot involves “growing” the core from a liquid at high temperatures. Once it reaches its desired size, the core is then removed from the liquid and coated with the shell.
How quantum dots get inside displays varies from manufacturer to manufacturer. Quantum dots can be combined with organic LED pixels, which emit color when activated by electricity. They’ve also been used in LED displays to produce a better white backlight and more color on screen.
There were 60 companies working with quantum dots in 2015, and the industry expects that number to grow to 97 this year, according to Samsung. They include research companies, materials suppliers and brands invested in the technology.
As a testament to the growing prominence of quantum dot technology, Samsung at CES 2017 unveiled three QLED TVs — a new line of 4K displays based on quantum dots that the company developed in association with Nanosys.
For the past several years, Samsung has been the largest strategic investor in Nanosys and works closely with the California company on research and development.
Now that Samsung has begun selling the QLED TVs, it is emphasizing the capabilities of the underlying technology to consumers.
“Most manufacturers make no mention of the technology,” Hartlove said.
Samsung gets quantum dots into QLED TVs by mixing them with a resin, creating a film — one layer in the flat-screen sandwich.
The TVs use metal quantum dots that do not contain cadmium, a toxic substance that has been used by other manufacturers, according to Samsung.
The Samsung dots enable QLED displays to produce 100 percent color volume, or all of the colors in a given color range at high brightness levels, the company said.
By comparison, in organic LED displays, color-rendering capabilities diminish as brightness levels go up, writer Mark Henninger said in a post for the audiovisual enthusiast site AVS Forum.
“I’ve consistently seen how the OLED stumbles when asked to render bright, vivid colors,” he wrote. “The reason for this is not simply that these LCDs render brighter specular highlights, it’s because they can reproduce a wider color gamut at high brightness levels.”
Samsung announced in February that independent tests conducted by a major technical association in Europe confirmed the color volume capabilities of the QLED TV, making it the first to obtain independent verification.
Televisions produced by Samsung last year were able to cover 84 percent of that range.
“Having a TV in your home that can reproduce all of the colors you’d expect to see in a movie theater with a professional-quality projector is pretty amazing,” Hartlove said.
Russ Banham, a Pulitzer-nominated business journalist and author of 24 books, writes frequently about technology.