Organic light emitting diodes, of OLEDs as they are more commonly known, are one of the most common display technologies we see in our lives. From TVs and phone screens to gaming monitors, OLEDs can be found in so many parts of our everyday lives.

OLEDs are primarily produced using a vacuum thermal evaporation (VTE) deposition process, which has its limitations as a shadow mask process is currently employed to manufacture side-by-side devices using red, green and blue colors (RGB) to produce white light and the image on the display.

This masking process is currently not scalable to the large sizes needed to make competitively priced TVs. The industry is looking at solutions that enable the side-by-side fabrication of RGB pixels over large areas. One solution has long been to print the displays using inkjet printing, which in principle would be more efficient and less costly, but to date, lifetime has been an issue.

Universal Display Corporation (UDC) is one of the leaders in OLED materials, supplying all of the largest players in the OLED display and TV market with its UniversalPHOLED phosphorescent OLED materials. Printing OLEDs has been of interest to the company, and with its novel Organic Vapor Jet Printing (OVJP), it has come a long way. In contrast to previous printing approaches, UDC is employing dry printing (vapor jet printing), as opposed to solution-based printing.

At the Society for Information Display (SID) Display Week 2023 International Symposium, Seminar and Exhibition, held from May 21-26 in Los Angeles, Universal Display highlighted its latest advances in its materials as well as the OVJP platform.

At SID Display Week 2023, Universal Display showed its OVJP system printed on a 200mm x 500mm Corning Astra Glass substrate, as well as the first-ever fully printed seven-layer (HIL/HTL/EBL/EML/HBL/ETL/EIL), 80 PPI, green commercial-level PHOLED device fabricated by UDC’s R&D OVJP.

“We are pleased to share our latest leading-edge phosphorescent material data and showcase significant milestone achievements with our groundbreaking organic vapor jet printing system at SID Display Week,” said Steven V. Abramson, president and CEO of Universal Display Corporation, in announcing the advancement.

“Scaling our dry printing technology to gen 4 while continuing to construct the building blocks of our alpha system and unveiling the first-ever fully printed PHOLED stack, consisting of 7 layers sequentially deposited with our OVJP platform, are important and exciting steps toward commercializing our trailblazing highly-efficient, cost-effective, high throughput manufacturing platform,” added Abramson.

One of the key attributes is that the system has comparable device performance with VTE. Dr. Michael Hack, VP of business development at Universal Display, said that these advances fit perfectly with Universal Display’s history as a technology innovator.

“In 1994, our founder and visionary, Sherwin Seligsohn, visited the electrical engineering school at Princeton University and he observed research by Drs. Forrest and Thompson in self-emissive organic materials,” Dr. Hack said. “He saw a green dot, with a 9-volt battery hanging from it, light up for seconds before it expired. From that green dot, Sherwin saw the future of display technology, and so began Universal Display’s story.

“We were founded with a vision of creating the next generation of displays, back when TVs were still CRTs (cathode ray tubes),” he added. “That technology was energy-efficient organic light emitting diodes, or OLEDs.”

In 1996, Universal Display became a publicly traded company with a research contract with Princeton University, three part-time employees and one patent pending.

“Fast forward more than two and a half decades and we have grown from an R&D start-up to a global leader in the OLED industry,” Dr. Hack observed. “Today, we work with the largest consumer display panel manufacturers in the world. Our proprietary technologies and materials can be found in virtually every commercial OLED product in the world, from smartwatches and tablets to smartphones and TVs. Our leading-edge phosphorescent technology is also key in OLED lighting. With over 15% of the world’s total electricity and 5% of worldwide greenhouse gas emissions stemming from lighting, more energy-efficient lighting products are in high demand.”

Universal Display and Printing

The UniversalPHOLED materials that Universal Display produces today are helping OLEDs to advance in the consumer market, and there is more to come.

“Based on our proprietary UniversalPHOLED technology and materials, OLEDs have the potential to offer power efficiencies that are greatly superior to incandescent bulbs and comparable with fluorescent tubes,” Dr. Hack noted. “The OLED industry is just beginning to take off, and we are excited to continue to have a critical role in this new era of energy-efficient display and lighting technologies.”

This brings us to the idea of printing displays. As easy as that sounds in theory, the reality is far more difficult.

“We have been working on printing OLEDs for a long time – everyone says it is the Holy Grail but producing it is difficult,” Dr. Hack reported. “Inkjet printing puts organic molecules into solution and prints it. However, the lifetime performance has never been the same as vacuum deposition processes, where molecules in powder form are evaporated.

“OLED TVs look fantastic but there isn’t a way to deposit side-by-side RGB pixels for large-area panels. Right now, manufacturers of small size displays use shadow masks for RGB molecules for each color,” said Dr. Hack. “Printing should be more efficient by putting the material only where you want it, which could be less expensive.”

With that in mind, Universal Display has worked on vapor jet printing for years. Dr. Hack noted that Steve Forrest, professor of electrical engineering and computer science at University of Michigan and a research partner at Universal Display, invented OVJP, which could jet print the OLED molecules from a gas phase rather than a solvent.

“With that, we became a lot more serious about OVJP because we believe that there’s a huge appetite for high-throughput, efficient, cost-effective maskless manufacturing of RGB side-by-side OLED printed TVs,” Dr. Hack said.

“This was initially an R&D project, but we realized to fully evaluate the idea, we needed to set up a company and scale the technology, so we set up OVJP Corp in California three years ago to demonstrate the feasibility of this technique over large areas,” Dr. Hack added.

Dr. Hack reported that leading display companies are intrigued by OVJP.

“We are discussing this technology with our OLED partners,” he noted. “This is a new approach – for example, LG uses an unpatterned white OLED and color filters to define RGB sub-pixels.”

The key is lifetime, as OLED TVs have to be long lasting and bright while being low cost. Universal Display is in discussions with equipment and OLED manufacturers, and the results have been very encouraging.

“At an R&D level, we now have reached the same lifetime for OVJP as vacuum deposition, and we are scaling it up,” Dr. Hack said. “OVJP offers enhanced performance, as there will be optimized side-by-side RGB pixels. We can use our same proven PHOLEDs for this process, which is one of the core attributes of OVJP.

“The greatest challenge was jetting vapors,” Dr. Hack continued. “In the early days, it was very hard to jet vapors and not have the molecules bounce off to other places. Printing a sharp line was an early challenge. We solved that several years ago by working on designs for jet heads, as the OLED deposition has to print accurately and end sharply. 

“I think it’s a very exciting technology with performance benefits,” Dr. Hack concluded. “It will set a new bar. OVJP could scale to all sizes of TVs. We are working to further develop this technology and demonstrate it to our partners.”