Technical / Research - Page 96

In June 2008, I interviewed Corey Hewitt and Dr. James Buntaine from Kodak OLED Systems.

Mr. Corey Hewitt is the co-general manager, operations manager and VP of Kodak OLED Systems. Dr. James Buntaine is the second co-general manager, and also the CTO and VP.

They were kind enough to send us an update on Kodak's OLED program and market outlook:

Kodak OLED Technology Update & Advancements

Kodak expertise and experience lies in material discovery, organic layer design, mechanistic understanding, image science, panel/module design, and manufacturing technology. These key value drivers associated with the Kodak technology, know-how and patents, maintain Kodak as an industry leader in enabling both the OLED flat-panel display and OLED solid-state lighting industries. Provided below are selected key areas technology and Kodak accomplishments:

Kateeva is a new startup, that has developed a new way to deposit OLEDs - using an inkjet printer and a micro-dryer called a T Jet (thermal Jet) along with proprietary inks. This will allow makers to use Gen 8.5 and larger substrates to make OLEDs.

Kateeva say that in four years (or more...) OLED TVs made using Kateeva's way will cost around 70% of what it costs to make a standard LCD.

Kateeva's T Jet sits between the inkjet nozzles and the substrate. The material is first heated to 100 Celsius to evaporate the carrier liquids. The remaining solids then get heated to 300 Celsius, turned into a gas, and deposited onto the substrate, where it solidifies.

A company called IP Mining corp has a new technology (ZeroBurn) that is capable of eliminating burn-in in plasma and OLED TVs. IP Mining are now looking to license this new technology to TV vendors.

 

Basically it works by monitoring each sub-pixel usage, and then stores a 'usage-profile' for each pixel. It then can change the inline video-signal to 'compensate' for the pixels that have been used more. There's also a mode in which the ZeroBurn runs under utilized subpixels until even luminance is achieved - but this seems like a waste of electricity, which will cause OLEDs to be very non-efficient!

IP Mining say that consumer TV content has changed dramatically over the last few years with
increased use of graphics overlays in news and sports programming and
the escalation of gaming time on the TV.

Novaled and Plextronics will jointly develop doped and solution processed OLED materials. The two companies will develop an advanced solution processable Hole Injection Layer (HIL) technology for OLEDs. By leveraging Plextronics’ organic conductive ink technology and Novaled’s organic dopant technology, the companies will target these advanced HIL materials for use with solution processed polymer and small molecule emitters, as well as with vacuum deposited small molecule emitters.

Novaled and Plextronics aim to offer a solution processed HIL with the same performance as a Novaled doped small molecule HIL deposited in a vacuum process. They will co-market Plexcore OC inks that incorporate Novaled dopany materials.

Sony has posted an interesting interview with Tetsuo Urabe (Senior Vice President, Display Device Development Group, Sony), together with 3 other Sony engineers received the 55th Okochi Memorial Award.

Tutsuo tells us how they started with a 13-inch prototype in 2001, the challenges in establishing mass-production of OLED displays, and the difficult work they had to do in order to meet the December 2007 shipment deadline.

Peptronics is an Israeli company, working on Polymer OLED materials. Their idea is to use a biological-based method to make the OLEDs. In the human body, we have 20 amino acids, used as building blocks for proteins. In the same way, they have made several "OLED building blocks", which can be used to create OLED materials, using Peptronics' peptide based technology.

Peptronics green OLED prototype

There are two types of OLEDs today: Small Molecules and Polymer based. Small Molecules are efficient and relatively easy to make, and are used in small displays today. But it is difficult to print them, and it is not easy to create a large panel using other methods. Polymer OLEDs are easily printable, and thus can be used to make large TVs - but their lifetime is short and they are less efficient.

Peptronics say that it will be possible to print cheap, large OLED TVs using their materials - which in fact will be printable (because they are polymer based), but also efficient - so it is the best of both worlds. The new materials can also be used for OLED lighting.

Peptronics are currently working on the finding the best "building-blocks" and creating numerous polymers from these building blocks using high throughput parallel synthesis. They then hope to sell their materials (or material-making systems).

OLED is an emissive display technology - which means that it emits its own light, in contrast to a reflective display - which uses an external light source - an ePaper display for example, or an LCD which is a display that blocks light from a backlight unit.

OLEDs are bright, and provide great image quality, and as of 2021, these displays perform very well under direct sunlight.

But this was not always the case. In early AMOLED displays, sunlight readability was very poor. The 2008 Nokia N85 for example, one of the first products with AMOLED displays, behaved very poorly in direct sunlight, as can be seen in the image below:

The problem in early AMOLED displays resulted from reflectance from metal electrodes in addition to relatively low brightness. Display makers however, soon upgraded their OLED displays to increase performance. Helped by new technologies and materials, OLED displays quickly overcame the sunlight readability problem. Today OLED displays actually perform better than the best LCDs in direct sunlight.

For more information on OLED display technology click here.

The CombOLED project together with CEA-LETI (a French research laboratory) has developed an efficient transparent white OLED. The Small-Molecule OLED has a 5 x 5 cm2 active emitting area, which is deposited using thermal evaporation and encapsulated using ultra-thin layers.

The OLED is 65% - 70% transparent, and emits light from both sides (bottom and top emission). The white luminance reaches 1000Cd.m² at 4 and 4.6 volts for bottom and top emission, respectively. The white OLED efficacy are respectively 11Lm/W and 3Lm/W at 1000Cd.m² for bottom and top emission, which leads to an overall efficiency of 14Lm/W. In this case the color coordinates are (0.40, 0.42) and (0.35, 0.42). When they create the same color for both sides, the efficiency is 10Lm/W and it's only 65% transparent.

The researchers are still working on greater efficiency and improvement of the permeation properties of the thin encapsulation layers.

UPDATE: Here's a video clip of the CombOLED transparent white OLED panel.

Kodak is showing a new demo of their flexible OLEDs - working under water:

Here's some closeups of the flexible OLED:

Scientists from the RIKEN center in Japan have found a new way to make OLEDs, using electrospray-deposited polymer films, which they say have better characteristics than OLEDs made from spin-coated films. The researchers have used a novel dual-solvent concept to make the electrospray-deposited films smoother than before, thereby enabling the superior devices to be built.

Previous attempts to use the electrospray-deposition technique for OLED fabrication have failed to produce polymer films that compete with other fabrication techniques. Yutaka Yamagata of the RIKEN Center decided to use a combination of two solvents to improve this technique, which uses a thin glass capillary with the polymer solution stored inside and a conductive wire inserted in it. When a high voltage is applied between this conductive wire and the OLED electrodes on the substrate, the solution sprays out of the capillary end as atomized droplets that are attracted to the substrate by electrostatic force. This means there is little solution wastage as the spray is highly directed.

From a series of comparative experiments, the researchers found that devices fabricated from electrospray-deposited films turned on at lower voltages and could support higher current densities than ones made from spin-coated films. At low voltages, the electrospray deposition also enabled higher pixel intensity.

We have discovered a range of conditions using a two-solvent method that can make extremely smooth thin films using electrospray deposition, says Yamagata. Using this technology these devices could be manufactured as inexpensively as printing newspapers.