TechBlick Highlights
We are publishing a series of two articles this week, highlighting the depth and breadth of innovation in the display industry. This article includes more than 40 individual images and charts showcasing various innovations in microLED, microOLEDs, quantum dots, printed displays, phosphors, TFTs, AI in displays, reflective displays, nanoimprinting, AR/VR and beyond. You can see the table of content for this article below.
In this article:
All the innovations highlighted in these articles are from companies presenting or exhibiting at our upcoming LIVE (online event) on Innovations & Market Trends in Displays. This event will take place in nearly two weeks, on 14-16 July 2021.
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Speakers Include
And many more...
Printed OTFTs: Finally coming of age?
OTFTs have been around for years. They were all the rage for years, but in recent years the interest has waned. OTFT technology suffered from low mobility (not enough above a-Si), instability (e.g., threshold voltage shift), and a lack of an application focus where it made sense. As IGZO and other amorphous metal oxide TFTs rose to prominence, attention moved away from OTFTs. Many big material developers stopped their research and offloaded their IP.
However, there are still very interesting works. In fact, we would like to highlight Smartkem. The basic core of the technology is a combination of high mobility small molecules and low molecular weight polymers, with solvents that allow the material to be applied as ink.
They are reporting 2cm2/Vs which is already above amorphous silicon. They can be deposited at low temperature (80C) on a wide range of substrates and can achieve very high levels of bendability (e.g., 5mm). As shown in the data below, the OTFTs can have ultra-low off current, comparable with IGZO. The stability has also improved.
There is renewed interest because Smartkem has shown that it can drive miniLED active matric backplanes which would enable dynamic local dimming, enhancing the competitive position of LCDs vs high-contract OLEDs.
Smartkem has shown that it can drive backlights with brightness levels up to 85,000 cd/sqm using a 2T1C TFT arrangement. This is interesting because amorphous silicon will struggle to supply enough current, LTPS can not be scaled to large areas, and IGZO is generally not easy to implement given the compositional/elemental uniformity requirements and can thus add to cost.
Smartkem is also taking steps to remove non-material related barriers against adoption too. It is implementing EDA tools to allow design of devices. It is setting up a foundry ecosystem. The process is compatible with amorphous silicon lines and the deposition of the organic material can be with slot die or spin coating.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Improving QY and Lifetime of InP QDs
According to RoHS rules, less than 0.01% of the substance by weight at raw homogeneous material level should be Cd. Since the active layer in QLED is homogeneous, then a non-Cd containing solution is required.
InP QDs have been making excellent progress over the years. This chart, by Nanosys, showcases the progress in quantum yield (QY) over the years.
In 2021, Nanosys reported a quasi-cubic InP/ZnSeS QD structure. The green InP QDs also show narrow FWHM (34nm) with a high QY (>95%). The quasi-cubic structure, it is argued, exposed only a Zn or S terminated facet, thus requiring only one type of passivation ligand. In spherical particles, multiple facets are exposed, ideally requiring multiple ligands. As such, it is argued, that quasi-cubic versions can have a lifetime x10 times higher.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
ZnTeSe chemistry: solution for true blue in QLED?
A challenge in blue QLED material selection is that InP QDs are suited to >500nm while common ZnSe QDs for <440nm. The ideal wavelength range is 440-460nm. As such, there is a gap for a Cd-free RoHS-complaint material.
An interesting material option is ZnTeSe. Here, as shown below, small amounts of Te doping can modulate the optical bandgap. As such, it is possible to synthesis narrow-band emitters with true blue emission wavelengths as shown below.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
QLED EQE and Lifetime Race: Latest Progress
Two important benchmarks are closely watched in the development of QLED: EQE and T50@100 nits lifetime. These parameters are not by any means sufficient in assessing technology readiness, but they do provide a useful indication of trends and direction of travel.
The charts below, updated by Nanosys, show that Cd-free QDs of all three colors (R,G,B) are making fast progress. Cd QDs are still in the lead on both fronts though. In particular, blue lifetime of Cd-free, even at a low 100 nits, is lagging behind by an order of magnitude.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
KSF vs InP for microLEDs: Latest Progress
The battle between red KSF phosphor and red QDs has been intense for some years. QDs have received much attention. However, red KSF has been steadily, and quietly, gaining commercial success in LCDs because it is narrowband and can be added directly to the LED given its high level of thermal and light flux stability. The chart below compares the market update of red KSF vs QDs in displays.
The battle between the two technology is moving to other fronts. A narrow band green phosphor is emerging which improves the FWHM of current phosphors, but may not be as good as many QDs. An emerging market is color converters for microLEDs. Conventional KSF phosphors are too large for microLEDs. However, as GE Research will show at TechBlick, the size of the phosphors is shrinking, potentially making them microLED compatible.
GE Research believes that the advantage of phosphors will become apparent when thick layers are required. This is shown below. This is mainly because QD’s suffer from self-absorption, and EQE will decline for thick layers. Thick layers may be needed for high light output to absorb sufficient blue.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Qualified green perovskite QD + red KSF phosphor film
Avantama discloses its latest work on the development of a film which contains both their shell-less ultra-narrowband green perovskites and GE’s red KSF phosphors. They have managed to mix these two different materials, with different brightness decay constants, into a film. In essence, they marry the best of QDs and phosphors, achieving >90% rec2020 and >99% DCI-P3 with high brightness (see chart below for performance positioning).
They are the first to achieve display qualification. The chart below also shows soe stability data under heat, light, and heat-light stress conditions.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Towards stable red perovskite QDs
Heilo Materials is developing perovskite materials. Uniquely, it is also developing red perovskites which have proved elusive due to its high instability.
The chart here shows the key proposition of red perovskites. It has a FWHM of 31nm, comparable to other technologies. However, the unique is that it continues to emit at red (631m) even when the particle size is large. In other words, unlike traditional QDs, its production will not require a tight control of the size distribution (note: red InP would generally need to be around 5nm with a tight size distribution).
Heilo Materials also discloses some stability data for the red QDs. These are impressive results but not yet close to the display qualification level. As shown below, the PL shows little change as a function of time and temperature exposure.
This excellent progress although it should be said that the red narrow emitter field is technologically somewhat crowded.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
PVD and inkjet printable TADF OLED materials with high PLQY
TADF (thermally activated delayed fluorescence) is a potential next-gen material technology for OLEDs. It offers high efficiency as it can harvest both triplet and singlet states. A major challenge that TADF seeks to resolve is a stable and high EQE blue emitters (phosphorescent OLEDs have excellent EQE but a stable blue has proved elusive). Furthermore, TADF also seeks to offer lower cost alternatives to red and green phosphorescent OLEDs which can also be inkjet printed.
An interesting capital-efficient Polish start-up, Noctiluca, is reporting interesting results for its blue TADF materials. In the below slide you can see a benchmarking (done by Noctiluca itself) showing how the PLQY of its evaporated and inkjet printed blue TADF materials compare with other commercially available materials.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Towards Gen5 R2P nanoimprinting for AR displays
There are many other uses of printing or R2R/R2P in the display industry. Another use case is in R2P (roll-to-plate) nanoimprinting for creating in- and out-coupling features for AV/VR glasses.
Such in- or out-couplings can be made on 300mm wafers, but the throughput is low. With R2P nanoimprinting the throughput may be substantially extended.
An interesting approach is by Morphotonics. Here, they tile together their nanoimprint stamps to create a Gen 5 R2P nanoimprinting line able to achieve sub-micron features and 480 eyepieces per imprint cycle. The R2P nanoimprint process requires solvent-free resins with high refractive index.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Rolling Nanolithography in Displays
Nanoimprinting can have many uses cases in displays also beyond AR/VR. One example is in development of highly transparent and high conducting metal mesh transparent conductive films.
One example is from Meta (Metamaterials) Inc. They have a rolling lithography system. Here, the UV light is wrapped within a soft rolled-up mask. The rolling nanolithography is used to create sub-micron exposures on a photoresist coated metal substrate. The photoresist is then etched, creating extremely high-resolution metal mesh.
The benchmarking chart shows that this process can create ultra transparent and highly conductive films. Currently the web width is 300mm but could be scaled to 1-1.2m.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Printable ultra-high refractive index materials for AR/MR and OLED displays
High refractive index materials are often needed in displays. In near-eye AR/MR displays they are needed in optical waveguides. In OLED displays or lights, they can improve outcoupling efficiency. They can also be use in 3D printed optics.
At TechBlick’s upcoming conference, you will hear from Pixelligent who has developed a range of high to ultra-high refractive index, UV curable resins for nanoimprint lithography (NIL) and inkjet applications.
The common material sets, as shown here, are titania (TiO2) or zirconia (ZrO2) nanoparticles which can be capped with different ligands for compatibility with various solvents.
The tables in the image also show their announced roadmap which will be discussed. There is a way to approach >2.0 refractive index using their titania nanoparticle chemistry.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Cholesteric liquid crystal: a commercial success story in R2R-made writing surfaces
Writing tablets use a Cholesteric Liquid Crystal (ChLC) fluid confined in a polymeric network that modulates the ChLC flow caused by the volume change due to the pressure applied during the writing process. The device is initially in a Focal Conic (FC) texture that allows light to go through to be absorbed and/or reflected by the background. Flow disrupts the FC texture reorienting the ChLC to a Planar (P) texture that reflects some of the ambient light in a Bragg selected wavelength.
Power is used only during the erase process thanks to the bistable properties of ChLC. Engineering the morphological and mechanical properties of the polymer network enables Kent Displays to create countless applications from handheld devices to large area boards under the Boogie Board brand.
The technology is thin, flexible, and low power. It is made R2R. The surface will be written on when pressure is applied to it using any tool tip, even a fingernail.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Visual Interface of IoT: fully printed R2R low-cost displays.
Printing plays a role also in simple (i.e., segmented) low-cost high-volume displays with applications in smart packaging and beyond. One example is in R2R printed electrochromic displays. A leading player here is Ynvisible. The image set on the left below shows snapshots of full R2R line (printer and converting).
This level of automated R2R production is a real progress in the field. The images on the right images show some application examples. There are numerous applications in smart packaging, IoT sensors, lowcost ubiquitous indicators, etc.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass.
Out of Home Displays: Requirements and Technologies
Out of Home (OOH) Advertising is a very old business that dates back to the time of the Egyptians. Pharaohs used obelisks to communicate and promote services to the public. In more recent times, OOH has evolved from the posting of Vaudeville ads on fences to crisp LED digital displays along streets and highways. The last 15 years have brought a surge in LED digital displays that allow for quick, dynamic content. An example, by Lamar Advertising, is shown below on the left.
This is an area with high potential for innovation. At TechBlick, you will hear from one of the main end users, Lamar Advertising, on how innovations with improved LED displays and reflective display technology along with solar and battery systems can shape the future of advertising displays.
Reflective outdoor displays that run on solar forever?
Reflective displays created e-readers and more. However, one reflective display technology is based on electrowetting display (EWD) technology. This technology has a long history of development but did not achieve the success that electrophoretic achieved.
EWD is now focusing on the outdoor signage market segment.
This is because it has potential a strong value proposition. The low power nature means that it can be powered endless on solar energy, saving installation, energy, and crucially maintenance costs. This will also mean that no digging will be required for installing power lines, batteries, etc.
At TechBlick, Etulipa, the technology leader in EWD based in Eindhoven, will be present the latest technology and application progress in this field.
To learn more join TechBlick’s upcoming LIVE(online) interactive conference on Displays & Lighting: Innovations & Market Trends (14-16 July 2021) with an Annual Pass
Part I:
The Depth & Breath Of Innovation In The Display Industry
Behind-display imaging and AI to shape the future of video conferencing
Laser-induced forward transfer & photonic soldering for large-area microLED displays
Xerographic-based digitally-controlled micro-assembly for microLED & microchip transfer
Enabling GaN LED epitaxial growth on large-area substrates (vs wafers)
Towards Mask-Free RGB high-PPI directly-patterned microOLEDs
Printing in tiling and transfer/placement of mini- and micro-LEDs
Setting benchmarks for evaluating the reliability of flexible/rollable displays