Quantum-Dot LEDs’ Victory over OLED TV Predicted, Debated at Advanced TV Conference
by Ken Werner
In his presentation at a recent conference on advanced TV technologies hosted by the Society for Information Display’s Los Angeles chapter, Seth Coe-Sullivan (co-founder and CTO of QD Vision) made a well-argued case that OLED TV will become irrelevant in 5 years. In that time frame, he predicted, conventional white LED (WLED) backlit LCD-TV will still be going strong, and quantum-dot-enhanced blue-LED-backlit TVs will be a major presence in the market place.
Coe-Sullivan (Fig. 1) was one of several industry experts who presented thought-provoking and sometimes conflicting views on the future direction of TV technology at SID LA’s “One-Day Conference on Technologies for Advanced Television,” held in Costa Mesa, California, on February 7, 2014. The conference was the 11th hosted by the chapter and was designed to provide display-industry professionals with opportunities for education, discussion, and networking.
Fig. 1: Seth Coe-Sullivan, co-founder and CTO of QD Vision, created a stir at the recent LA Chapter conference by predicting the demise of OLED TV. (Photo courtesy Ken Werner)
According to Coe-Sullivan, the TV tech-nology that will follow the above-mentioned LCD variations will be quantum-dot LED (QLED) technology, which has the same general structure as OLED technology but with quantum dots as the emissive layer instead of organic light-emitting materials. Coe-Sullivan’s argument was based on the ability of quantum-dot-enhanced LCDs to provide better color gamut than OLED displays and also to reduce power consumption, all at a minimal increase in cost. Coe-Sullivan systematically countered all but one of the arguments made in OLED TV’s favor – its very high contrast ratio in a darkened room.
One of OLED TV’s problems has been cost, which has kept its market penetration low. Although not widely recognized by the general public, quantum dots appeared in major products in 2013: three models of Sony television (in the U.S.), which use QD Vision’s Color IQ rail, and one of Amazon’s new Kindle Fire HDX models, which uses 3M’s quantum-dot enhancement film (QDEF). Coe-Sullivan, 3M’s Erik Jostes, and Touch Display Research’s Jennifer Colegrove all predicted a rapid growth in design wins for quantum dots in 2014, with increasingly rapid growth coming in 2015 and following years.
Coe-Sullivan’s case was well laid out and generated a very lively Q&A session, but none of the other speakers, including 3M’s Jostes, defied the conventional wisdom that predicts OLED TV’s continuing growth. In addition to discussing quantum dots in general and QDEF in particular, Jostes spent a significant amount of time discussing which display characteristics viewers respond to most strongly. To make prediction of display-quality preferences easier, 3M has developed a single metric, the Display Quality Score (DQS), which incorporates the usual individual metrics – resolution, viewing distance, display size, color gamut, and contrast – as well as the relative importance viewers give these metrics in actual testing (Fig. 2). (For more about 3M’s quality metrics, see the article “PQM: A Quantitative Tool for Evaluating Decisions in Display Design,” in the May/June 2013 issue of Information Display magazine.)
Fig. 2: Extensive development and testing have gone into 3M’s Display Quality Score. This is an example involving luminance. (Image courtesy 3M)
The metric has been verified in validation studies. Resolution has the biggest impact on DQS, and color has the second biggest impact, according to Jostes, who also said, “people generally prefer high saturation to fidelity.” Jostes also noted that at a 14-in. viewing distance, improvements in DQS top out
at about 500 ppi, which has clear implications for how much pixel density makes sense in tablets, phablets, and smartphones.
Ho Kyoon Chung, in “Why is OLED-TV Taking So Long,” countered Coe-Sullivan’s arguments about OLED TV’s eventual success, making the case that OLED TV’s problems are being resolved. Chung, Chair Professor at Sungkyunkwan University and Director of the Samsung SMD OLED Center at the university, was formerly Executive VP at Samsung SMD and exhibited an impressive depth of knowledge about OLED technology and manufacturing issues, as well as a genial style of presenting what he knows.
Chung concluded that OLED TV has suffered from significant yield issues that are now in the process of being resolved. He commented that LG Display probably had a 10% yield for TV panels in the middle of last year, and probably now has a 50% yield.
Low yield is one of the things that keeps costs (and prices) high, and price is the main thing that is slowing OLED TV’s market penetration. Another issue is that processing costs, apart from yield, remain high. However, said Chung, OLED-TV manufacturing technology will converge to standard techniques, such as white OLED plus color filter and fabrication by printing. With convergence and scale-up, the cost of manufacturing OLED TVs can be less than that for LCD TVs, he maintained. He concluded by saying the critical innovation for low-cost OLED manufacturing will be roll-to-roll manufacturing and rollable TV.
At the moment, it is ultra-high-definition, or 4K × 2K, television that is moving the TV market. Some analysts are waving red flags, saying that lack of conveniently available native 4K content will put the brakes on UHD sales, as lack of 3-D content in part put the brakes on 3-D viewing. But in “Technicolor 4K Image Certification,” Technicolor’s Kirk Barker outlined the algorithms that implement very-high-quality 2K-to-4K up-scaling, and Technicolor’s program for certifying the efficiency of chips and end-user products that implement such algorithms. Barker noted that in side-by-side tests at CES and elsewhere, analysts and journalists often mistakenly select the up-converted image over the native 4K image. As a participant in more than one of the tests, yours truly can support Barker’s report.
Sharp Electronics has made IGZO metal-oxide TFTs a commercial success in high-pixel-density LCDs, but there are still complications in applying them to OLED TVs, as LG Display has discovered, although yields are reportedly rising. Sharp Senior Product Marketing Manager Dave Hagan explained how IGZO not only supports high pixel density in LCDs, but also enables power saving and more-effective touch panels because it supports a less-noisy backplane than does amorphous silicon (Fig. 3).
Fig. 3: Sharp’s Dave Hagan did not hide his enthusiasm for the company’s IGZO-based displays. (Photo courtesy Ken Werner)
The original attraction of metal-oxide TFTs was that the amorphous version offered almost as much carrier mobility as the crystalline state. But now we have seen that the amorphous version has stability problems. Hagan suggested that Sharp is developing a crystalline structure that will further stabilize IGZO and support displays with over 500 ppi. The new material has higher electron mobility and supports lower power consumption than the current amorphous material.
In addition to IGZO’s use in LCDs and OLED displays, Hagan noted its application in the Pixtronix in-plane MEMS display that has been under development for some time. Hagan suggested that we may see a commercial product from Pixtronix in the second half of this year. There may be more definitive information at SID’s Display Week, where Sharp and Qualcomm/Pixtronix will almost certainly be exhibiting.
SID LA’s One-Day Conference on Technologies for Advanced Television was characterized not only by high-quality speakers who presented effectively, but also by a
high-quality audience that sustained spirited and good-natured interaction with the speakers. The format, well-honed over 11 conferences, also provides comfortable
opportunities for conversation and networking. •