Quantum Dots Get Hot

At Display Week quantum-dot makers had more significant announcements and introductions than many of us expected.

Its not that QDs had become boring before Display Week. After all, television market penetration was 25% heading toward 50%; and the combination of quantum-dot-enhanced backlights, wide color gamut, and high dynamic range had sharply narrowed the visual difference between LCD- and OLED-TVs and opened a niche for expensive premium LCD-TVs.

Low Overlap in Red Quantum RodsThere is very low overlap between the absorption spectrum (solid line) and emission spectrum (dotted line) for red quantum rods, resulting in low quenching as the concentration of the rods increases. A similar plot is obtained for green rods. (Figure: M. Suzuki, “Quantum Rod Containing Film Development for Display Applications,” P. 340-43 SID 2016 Digest, Society for Information Display, 2016)

But that was just the first wave. At Display Week Nanosys introduced and demonstrated its Hyperion quantum dot system, which matches the performance of cadmium selenide quantum dots while being officially “cadmium free” under RoHS regulations, said Nanosys Corporate Communications Manager, Jeff Yurek. The Hyperion approach combines a completely cadmium-free red quantum dot with a green dot that contains very little cadmium. A QDEF sheet using the new formulation has a cadmium level less than the 100 parts-per-million limit set by the European RoHS Directive, so no exemption is required.

In a paper delivered at the SID symposium, Nanosys R&D VP Charlie Hotz said that an Hyperion QDEF sheet provided over 90% of the BT.2020 color gamut, just as conventional cadmium selenide (CdSe) quantum dots do. This was supported by a side-by-side demonstration in the Nanosys booth. So, if their are no unforeseen difficulties, panel makers and TV manufacturers (such as Samsung) will not have to choose between high-performing and more efficient CdSe dots and the less effective but RoHS exemption-free indium phosphide (InP) dots. (Although my understanding on this is that Samsung rejects cadmium completely for historical reasons – its decision is not based on an exemption – although the lack of QD use from auto makers is because of the need for an exemption – BR)

Nanosys says QDEF manufacturing partners will be evaluating the new materials in Q3’16, with volume production of Hyperion QDEF expected in early 2017. Hartlove said there is no cost differential between Hyperion and CdSe dots, and that the manufacturing costs of Hyperion are actually lower.

Wait! Did I say partners with an “s”? Isn’t 3M Nanosys’s only QDEF manufacturing partner? Well, it was. At the beginning of Display Week, Nanosys announced it was partnering with Hitachi Chemical to develop QDEF films for display applications.

That brings up another question. Isn’t QDEF (Quantum Dot Enhancement Film), an acronym that goes so well, with 3M’s BEF and DBEF, the property of 3M? In fact, it isn’t. Nanosys owns this trademark.

In a press release issued on May 23, Hiroyuki Morishima, the GM of Hitachi Chemical’s R&D Headquarters, was quoted as saying “We plan to begin shipping product in mass production volumes during the second half of 2016.”

During a booth tour for institutional investors sponsored by Sanford C. Bernstein (Hong Kong) Limited, Hartlove said QDEF is selling for $60 per square meter, and that 200 million square meters were sold in 2015.

QDs to Eliminate Colour Filters?

In addition to these planned major announcements, Nanosys added an unplanned one when CEO Jason Hartlove apparently went “off the reservation” at the Business Conference and announced the development of quantum dots that are stable in air thanks to individual encapsulation.

Quantum dots are sensitive to oxygen and moisture, and commercially available quantum-dot products, such as QD Vision’s Color IQ linear device and Nanosys’s QDEF film, have componentsthat protect the dots from air. But with each dot snug in its individual encapsulation, significant new uses become possible: electrical, instead of just optical, excitation; ink-jet printing; and even gravure printing, according to Hartlove. To prove it works, Nanonsys’s Jeff Yurek provided a lab-bench-style technical demo behind a closed doors in the Nanosys booth.

An exciting application is making an LCD color “filter” by ink-jetting patterns of red- and green-converting quantum dots on a film that sits in front of a blue direct-addressed backlight. Instead of inefficiently blocking light with a conventional color filter, you would be converting the blue light to red and green where you wanted it to make full-color pixels. Yurek suggested a possible efficiency improvement of 2 to 3X.

Yurek said there is a “huge pull” from a customer who would like to go market with an air-stable based product in 2018, but Nanosys thinks 2019 is more likely.

Nanosys vs QD Vision

At Display Week there was also considerable discussion — at least among the media and analysts — about an April 14th press release announcing Nanosys’s filing a lawsuit against competitor QD Vision for patent infringement. The release is notable for its very strong language, which includes the following quote from Jason Hartlove: “QD Vision is a poor imitator using technology stolen from Nanosys to produce cheap knockoffs. When QD Vision’s own technology failed, the company chose infringing on Nanosys’ patents over taking the time to innovate,” said Jason Hartlove, President and CEO of Nanosys. “The results speak for themselves. Products using QD Vision’s solution have poor color uniformity*, high defect rates in the field and unfortunately, are creating the perception that Quantum Dots are a cheap and inferior quality technology. If consumers come to associate this level of performance with Quantum Dots, then the reputation of the technology in the marketplace will be permanently tarnished.”

That’s strong stuff. What is indisputable is that the TV industry’s transition from edge-lighting to direct backlighting in larger sets has strongly favored the Nanosys/3M (and, now, the Nanosys/Hitachi) film-based approach over QD Vision’s linear element, which was designed when edge-lighting dominated.

Finally, Nanosys was promoting President Obama’s award of the National Medal of Science to company co-founder Paul Alivisatos for his work on quantum dots.

QD Vision Delivering Commercial Products

Given the transition from edge-lighting to direct backlighting it came as no surprise that QD Vision is working on a film-based approach with a partner, but the company’s emphasis at Display Week was how cost-effective the company’s ColorIQ thin-tube quantum-dot optic can be in smaller displays.

In its booth, QD Vision was introducing the Philips 276E7 27-inch, 1920×1080 monitor to the U.S. market. The monitor displays images with 250 cd/m² luminance and 99% of the Adobe RGB gamut. The Philips monitor brand, which is controlled by TPV’s MMD subsidiary, has been sold primarily in Europe and Asia, but TPV plans to make a marketing push in North America, too.

AOC 27 inch QD MonitorThis AOC 32-inch monitor with QD Vision ColorIQ optic is currently available in China. The similar 27-inch with 99% Adobe RGB gamut, 250-nit peak luminance, and FHD resolution is now available in the U.S. for about $300. (Photo: Ken Werner)

Also announced was a 27-inch monitor from TPV-owned AOC, which has specs similar to the Philips 27-inch. It will be available in North America Q3 at a price that will probably be close to $300. The LEDs, and the ColorIQ optic, are on the bottom edge in these monitors. QD Vision executives stressed that ColorIQ can be very cost-effective for consumer monitors and smaller TVs.

Other ColorIQ monitors and small TVs being introduced in the booth were a 24-inch AOC monitor, a 24-inch Philips monitor, and 32-inch Philips and AOC monitors currently available in China.

QD Vision execs said the company continues to work on QLED (a structure in which the quantum dot material is electrical rather than optically excited, and is therefore suitable for an emissive display that could compete directly with OLED). The company believes that QLED is the ultimate display, and they expect to be making product in two years. The company continues to develop the demanding dot-on-chip, “if not for LCD then for lighting.” Quantum dots for mobile phone displays will have to be dot-on-chip, an executive said, since there is no room for anything else.

QD Vision had a side-by-side comparison of four TVs: QD Vision CdSe film (105% NTSC), InP film (91%), OLED (82%), and standard white-LED-lit LCD (72%). It’s no longer a surprise to anyone that CdSe quantum dots outperform InP dots, and the difference is easy to see. The very poor showing of the OLED-TV was more surprising. In a recent Display Daily, OLED Association Managing Director Barry Young suggested that an older model OLED-TV was being used for the comparison. (Drinking the QD “Kool-Aid”)

Analyst Comment

My main take-away: cost-effective quantum-dot consumer monitors are here, and with TPV supplying about half of the world’s monitors, were are likely to be seeng a lot more of them.

Roughly spherical dots are not the only form in which quantum particles come. The directional characteristics of quantum rods open new applications in color filters and other products, said Bob Miller of EMD. In an invited paper entitled “Quantum-Rod-Containing Film Development for Display Applications,” Merck Japan’s Masayoshi Suzuki discussed some of the details. Among them is that Q-Rods have a smaller overlap between the absorption and emission spectra than Q-Dots, which means there is less quenching of the output when the Q-structures become more concentrated. There is also a higher-outcoupling efficiency because the distribution of emitted light is directed more toward the normal to the film plane.

As influential as quantum dots have already been, we can look forward to dramatic technical developments and impressive market growth. — Ken Werner

My own experience of the first Philips QD-enabled monitor was that it suffered from poor uniformity, although that was a sample of one. (BR)

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