Kateeva finally unveil their YIELDjet OLED TV inkjet printing system

Kateeva is a US based startup that was established in 2009 to develop OLED ink-jet deposition technology originally developed at MIT. The company has been been in stealth-mode for years, and now finally they have unveiled their technology and system, branded YIELDJet.

So YIELDJET is an inkjet printing system that can be used to produce OLEDs in high volume. Kateeva claims that their system, the first one engineered from the ground up for OLED mass production, will dramatically improve yields and drive production costs lower. Kateeva says that this was achieved by three major technical breakthroughs: is features a production-worthy pure nitrogen process chamber, which doubles the lifetime in certain applications, it reduces particles by as much as 10X thanks to a specialized mechanical design and it offers exceptional film coating uniformity with a process window that’s 5X wider than standard technologies.

Kateeva already has R&D tools deployed at customers sites in Asia, and are now working towards full-scale commercialization systems. We have discussed Kateeva's technology and business with Dr. Conor Madigan, the company's President and Co-founder.

Q: Dr. Conor, thank you for this interview. We're happy to finally see Kateeva come out with a commercial production system. Let's begin with some technical questions. Can you disclose the kind of materials you can print in YIELDjet systems? Are both SM-OLEDs and P-OLEDs supported?

Yes, both SM and P-type materials can be printed. To achieve good results, we work with various material suppliers to cooperatively optimize ink, process, and equipment. However, to be clear, we make equipment, not ink. Our cooperation strategy is to help develop a strong ecosystem of reference inks and processes so that customers can quickly realize inkjet OLED mass production on our equipment.

Q: Is it possible to print all organic stack layers using YIELDjet? Shall we expect gradual adoption (for example only emitters and top layers at first, etc) or do you think this will be an all-in adoption?

We are seeing two main inkjet OLED strategies. In one case, hole inkjet layer (HIL), hole transport layer (HTL), and RGB emitting layer (EML) are printed. In another case, HIL, HTL, and RG EML are printed. In both cases, after printing, the substrate is placed into a vacuum deposition system to finish the device. The finishing steps do not require fine pixel patterning, only blanket coating. In the case that only the RG EML materials are printed, a B EML material is coated over the entire display. With proper stack design and material selection, the RG pixels will still emit RG, and the B pixel will emit B. This is the so-called “hybrid” or “blue common layer” approach. This has the advantage of offering VTE B EML performance, which historically has had higher lifetime than inkjet B EML performance.

In the case that RGB EML materials are printed, there is no need to coat a B EML over the device. Once the EML coating is finished, the finishing steps involve optionally coating one or more additional blanket organic layers (e.g. hole blocking layer [HBL] and/or electron transport layer [ETL]) and the cathode).

Kateeva pilot platform

We have seen some work from material developers on inkjet HBL and/or ETL materials for coating over the EML, but this is not close to production worthiness. There is also some work on developing inkjet conductors as top electrode materials, but again, this also is not close to production worthiness.

Q: It is also possible to print OLED encapsulation layers with your system. This is one of the major challenges towards flexible OLEDs that do not use glass barriers. Can you explain your encapsulation technology?

Many customers are exploring multi-layer thin-film encapsulation technologies to solve the flexible encapsulation problem. These multi-layer coatings combine one or more organic layers with one or more inorganic layers (e.g. oxides, nitrides, and/or metals). Current techniques used to deposit the organic coating layer, are expensive, slow, wasteful of raw material, and low yielding due to particle defects, largely because of the need to form a patterned coating that is uniform over the active area while leaving the electrodes clean for later attachment of the external display drivers.

Kateeva's inkjet platform is well suited to depositing this patterned organic coating layer inexpensively with excellent uniformity, high speed, high raw material efficiency, and low particle contamination. Another unique characteristic of this application is the necessity of printing in a nitrogen environment, since the encapsulation process has strict requirements for low oxygen and moisture contamination, and nitrogen is a key advance of the YIELDjet platform.

With YIELDjet, inkjet can rapidly move into flexible OLED mass production as part of the thin-film encapsulation portion of the production line, and help drive down costs by driving up yields and productivity.

Q: Can you disclose how precise this printing process is? What's the highest PPI that can be achieved?

We have focused on TV applications for our work on inkjet printing of the OLED device layers. When using the conventional side-by-side RGB pixel layout, Kateeva's standard printing technology can provide sufficient precision for 4K x 2K displays at the 31” size and up (e.g. ~120 ppi).

We also developed an approach for inkjet printing much higher resolution displays (e.g. ~400 ppi) for mobile applications using novel pixel layouts more tailored to inkjet. While we still view TV as the most important market for inkjet, we are starting to see strong customer interest in our high-resolution technology as well.

Q: We know you are developing a Gen-8 system. Is that for a specific customer? Can you say what will be the capacity of such a system and whether this is a commercial one or a pilot one?

The G8 system we are building can be configured as a full mass-production tool for deposition of a single layer (e.g. HIL, HTL, or RGB EML), with between 90s and 120s total average cycle time (TACT) depending on the number of inks used for each layer. It can also be configured as a pilot tool for printing all layers (HIL, HTL, and RGB EML), with a TACT for each layer of 300s.

In the pilot configuration, the first layer would be printed, the substrate would move to a drying and baking system, and then the substrate would be returned to the printer for printing of the second layer, and so on. To our knowledge, this is the only G8-scale system that offers customers the ability to print all of the layers with a single printer, thereby greatly reducing the customer investment and footprint needed for an inkjet OLED TV pilot line.

When we deliver this system, we expect that it will be provided in the pilot configuration.

Q: Did you develop the inkjet printhead in-house or do you use 3rd-party ones?

We work with third-party printhead suppliers. In general, we use printheads based on standard models with various proprietary customizations to improve performance for each of our target applications.

Q: Soluble materials have traditionally been less efficient and durable than evaporated materials. Do you think soluble materials are finally ready for commercial adoption in TVs?

Evaporation materials continue to have superior device performance, and we believe evaporation will continue to have superior performance in the future. The gap is closing, however, and in our view evaporation is a dead end for TV mass production. So the critical question is what is the performance needed for the first commercial TV products and when will solution materials have that minimum level of performance.

Based on our work with material partners, we believe soluble materials are already good enough for Pilot product evaluations, and will be able to match the performance of the current low-volume evaporation-based 55” TV products within the next 18 months. Furthermore, we see steady improvement in solution material performance continuing for the foreseeable future – there is no indication that performance improvements have stalled or reached a ceiling. So we now feel confident that solution materials are on track to meet the needs of commercial TV mass production.

Q: Can you give an estimate to the cost save of YIELDjet over current evaporation technologies? How much do you think will a 55" printed OLED TV cost?

In our cost modeling, we focus on the comparison between projected LCD panel cost and inkjet OLED panel cost, as ultimately LCD is the real competition for inkjet OLED TV.

Based on our modeling, with YIELDjet, OLED manufacturing costs have the potential to be 30% LOWER than LCD. While it will take some time to reach this level of manufacturing maturity, the critical benefits of YIELDjet – i.e. enhancing yields and providing inkjet’s inherently greater scalability and high material efficiency – will immediately offer substantial cost reductions for manufacturers and will put OLED on the path toward achieving its full low-cost potential and ultimately replacing LCD as the leading TV technology.

Q: If all goes well, when can we expect the first OLED displays printed with YIELDjet systems on the market?

It’s premature for us to talk of product shipments. And, of course, we can’t speak for customers on their production plans. Today’s news centers on the YIELDjet platform – the core technology upon which our future products will be based. We’re excited to hit this milestone. It marks Kateeva's transition from R&D to commercialization. But, count on hearing more from us on products in the coming months.

Dr. Conor - thanks for your time, and good luck to both you and Kateeva! Hopefully we'll hear more news regarding your technology and systems in the future.

Disclosure: Kateeva is an OLED-Info sponsor

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