Spin coating

Hitachi Research Laboratory (HRL) unveiled a new prototype OLED lighting panel that was made using a single-stage coating process. Hitachi developed a new self-organized "spontaneous multilayer light-emitting layer formation material" which is a mix of RGB small-molecule emitter materials. The process simply coats the panel once with this material and then the three different layers (red, green, blue) are automatically formed in the correct order.

The three emitter dopants use the same host material. HRL still managed to create a very efficient OLED (up to 70 lm/W, with a light extraction layer). Eliminating two steps from the deposition process using this new coating technique and materials will theoretically enable cheaper panel production.

Heraeus is introducing new polymer OLED materials. The HIL-E grades is a combination of Hole Injection Layer and a high conductive electrode - and so provide an economic ITO alternative. These are PEDOT formulations designed for the OLED lighting industry.

The HIL-E materials feature excellent planarization properties and a refractive index that matches glass and plastic substrates. The formulations are also pH neutral. Regular and high work function grades are available. These polymer-based materials are suitable for slot-die coating, ink-jet printing and other deposition processes.

Mitsubishi Chemical and Pioneer have jointly developed OLED elements produced using a wet coating process for the light-emitting layers. The two companies will establish a testing facility with an aim to commercialize this technology for OLED lighting mass production by 2014.

Mitsubishi's and Pioneer's OLED coating project began in January 2010, and in May 2011 the companies announced that they managed to fabricate a white OLED in which the emissive layer was formed in a coating process. That OLED featured 52 lm/W and a lifetime (LT50) of 20,000 hours (@1,000cd/m² luminance). The new panel produced now features 56 lm/W and a lifetime (LT70) of 57,000 hours (@1,000cd/m² luminance) which is quite an improvement.

The Holst Centre and Solvay report advances in flexible OLED lighting panels. They present a bendable 69 cm² OLED panel that features 30 lm/W efficiency at 1000 cd/m²:

Dupont has unveiled two new OLED display prototypes made by a coating process (using solution processable materials). The first (shown below) is a 4.3" 480x272 (128 ppi) and the second is a 5.8" display offering 294x196 (83 ppi).

Dupont says that the solution-processable displays offer better uniformity than commercial LCD displays. The cost advantage for solution-processable OLEDs grow as as the panel size increases.

The Printable Electronics Technology Centre (PETEC) has announced plans for a new prototyping line to support the lighting and Organic Photovoltaic sectors. The new line is targeted at industries needing large area coating capability alongside the need for reproducible uniform and low defectivity thin film coating onto glass and plastic substrates.

It is designed to be an automated batch tool based on cassette handling of samples to minimise manual intervention. The specification has been aligned with the needs of the SSL and PV industry. It will produce up to 20 samples per day with a panel size from 100mm to 200mm square. The line will have slot-die and spin coating modules, metal and organic evaporation and encapsulation.  It will enable the deposition of solution and small molecule OLED material technologies. It will target fine coating active layers of 10-200nm thinness with uniformity of +-5% across the full panel width.

Last week we reported that PolyPhotonix plans to launch a 8" 60lm/W OLED Lighting panel. They will be using this line at PETEC.

In February 2009, we interviewed Dr. Udo Heider, Merck's OLED Unit VP. Merck is a global pharmaceutical and chemical company based in Germany, working on high performance OLED materials. Dr. Heider was kind enough to do a follow-up interview with us...

Q: Dr. Heider, thanks for taking the time to do this second interview... Back in February you said that within nine months you'll have a solution-processable Green OLED ready. Any updates on that? What about Blue and Red?

Indeed it is with great pleasure for me to report that our development team has really done an excellent job in making progress and delivering results in the area of solution-processed OLED materials. Merck can now report that in a spin coating process, the gap between solution and evaporation processed phosphorescent green materials has been almost completely bridged. Merck is now shifting its focus to the implementation phase: this means working together with world renowned process and display manufacturers to make sure that these materials can now be printed in line with performance and yield requirements. We hope to report on results in this area in the near future. The extensive know-how that has been accumulated during the last couple of months in the areas of Green can now be transferred with confidence to the other primary colors Red and Blue. The key to success is based on combining the learnings and strengths of the Small molecule and Polymer OLED worlds.

CDT is one of the leaders in OLED research, focusing on Polymer-based OLEDs (PLEDs, also called P-OLEDs). While these OLEDs are lagging behind small-molecule OLEDs in current products (all AMOLEDs today are based on SM-OLEDs), some companies believe that PLEDs are actually the better tech for the future.

CDT's CEO, David Fyfe has agreed to answer a few questions we had on CDT's technology. David joined CDT in 2000 as Chairman and CEO. David saw CDT go public in 2004, and then negotiated the sale of CDT to Sumitomo for $285 million (in September 2007). David is also a director of Soligie, an electronics printing company, Acal Energy, a fuel cell technology developer and the Plastic Electronics Foundation.

Q: David - thanks for agreeing to do this interview. Since the Sumitomo acquisition, CDT has been rather quiet... can you give us an update on where's the company now, and where's it is headed?
Since the merger of CDT into Sumitomo Chemical in September 2007, CDT has grown substantially and received considerable capital investment to enable it to remain a leading developer of PLED technology. It works very closely with SCC laboratories in Japan and most recently has been transferring manufacturing process knowhow to SCC's own PLED manufacturing development line, recently commissioned at Ehime on Shikoku, Japan. CDT in partnership with SCC has made large strides in materials lifetimes and efficiencies. SCC prefers to take a lower profile in announcing these advances since its business model is to work with selected display maker partners in a collaborative, confidential relationship. We have also made big strides in the development of top emitting structures and in printing PLED displays. SCC's strategy is that CDT will continue to be its leading development center for PLED technology with Ehime scaling process technology to a yielding process status. CDT is also working very closely with Semprius of North Carolina, USA to develop single crystal silicon TFT structures on which PLED devices can be deposited and driven using Semprius’ proprietary stamping technology.

Q: It seems that OLED displays are finally entering the mainstream - we hear of new devices (mainly by Samsung, but also from Sony, Microsoft, LG and others) almost daily. What are your thoughts on this? what are the challenges that still exist for OLEDs?
Sony broke the logjam of resistance to the adoption of OLED in large displays by major display makers with the introduction of its XEL-1 11 OLED TV in 2007. Samsung SDI’s investment in small screen OLED production in 2007, based on LTPS backplanes was another major impetus. Since then, Chi Mei has brought on small OLED screen capacity, TMD (now wholly owned by Toshiba) has built an OLED line to manufacture small screens, LG Display will start up their Gen 3.5 line late this year and if press reports are to be believed, Toppoly will commission their capacity with Nokia as a lead customer and Panasonic have a major OLED development program for large OLED displays.

Data from spin coated devices using a common cathode and interlayer material demonstrate lifetimes for recently developed solution-processable green and red PLED materials of 78,000 hours and 67,000 hours, respectively, from an initial luminance of 1000 candelas per square meter, or cd/m2. This is equivalent to approximately 445,000 hours and 420,000 hours from an operating brightness of 400 cd/m² for these materials.

These latest lifetimes represent a 60% and 280% increase in performance for green and red materials over results that were announced in May and March of this year, respectively.

Cambridge Display Technology and Sumation are pleased to announce new and improved results for green and blue PLED materials.

Data from spin coated devices using a common cathode and a recently developed solution processable green PLED material demonstrate lifetimes(1) of 50,000 hours from an initial luminance of 1000 candelas per square meter, or cd/sq.m. This is equivalent(2) to over 285,000 hours from an operating brightness of 400cd/sq.m for this material and represents a 40% increase in lifetime compared to results announced on March 27, 2007.