Another virtual conference in the books. This time the OLED Summit. Just like last year, there were a few talks on EL-QLED devices as the OLED community wants to keep tabs on the competition (I suspect). I had intended on sharing my thoughts on the OLED summit with you earlier, but I felt compelled to share with you last week the news about EL-QLED progress comes out of the “blue.” So now I’ll back track a few weeks to the OLED summit where, on my count, there were two talks focused exclusively on QLED, and QDs were mentioned in a handful of other talks. Since the OLED portion was covered last week I will focus my efforts on the QD highlights.
The two companies in attendance strongly representing EL-QLED technology were Nanosys and TCL. Both are pioneers in the field. Here I’ll try to make sense of all the data presented at the OLED summit, SID Display Week, and recent literature (specifically Samsung’s articles on red and blue Cd-free devices) into an all-encompassing look at the current status of this technology.
TCL is taking a different approach than many other companies. They have not strayed from their focus on Cd-containing QD devices. It is not surprising that these devices show much better performance than their non-Cd cousins, and TCL leads the way when it comes to lifetime of these devices. An important distinction here that is very important to call out is the metric used for lifetime. TCL is using T95 at 1000 nits. This is 10x the luminance of the non-Cd devices I recently reported on, and the end point (95% of initial emission) is a far stricter (and more realistic) metric than the T50 which the non-Cd EL-QLEDs are currently reporting. The T95/1000nits value is more akin to what display makers will require of QLED devices, so seeing numbers over 10,000 is very encouraging. As I have mentioned before, red is the closest to being commercially ready, with lifetime of 10-20k hours depending on the method of deposition (according to TCL’s latest results).
As you can see, the best values are achieved upon spin coating (“spin” in the table above). Spin coating produces extremely thin, uniform layers of QDs which results in better performance. But it is not a viable approach for a large display. Ink jet printing (“IJP” in the table above) is a scalable approach to manufacturing EL-QLED devices, and it is encouraging that the red performance using IJP is approaching the performance of a spin-coated device. It appears that the blue and green IJP results were not worth sharing, so clearly there is work to be done.
TCL shared their own historical progress in blue QLEDs, which as you can see from the graphic below has shown rapid progress in the past 2 years from <1 hour lifetime in 2018, to >300 hours as of late 2019. I presume it’s even higher now.