Advances in UDC’s OVJP offer an alternative path to lower-cost, higher-performance large-area RGB OLEDs

In this commentary, Practice Leader Charles Annis provides an in-depth analysis of UDC's organic vapor jet printed (OVJP) technology, a pixel patterning process, which carries potential advantages over current OLED technologies but remains a few years away from commercialization.

Universal Display Corporation (UDC) is a leading company specializing in research and development (R&D), production, licensing, and support of organic light-emitting diode (OLED) materials. The company has been developing a unique side-by-side pixel direct patterning technology called organic vapor jet printed (OVJP) for many years. UDC has highlighted the technological advantages and opportunities that OVJP presents in corporate presentations and, over time, has released more information about OVJP as it continues to progress on its pilot tool.

During the Society for Information Display’s (SID) Display Week 2023 in May, the company showcased a significant milestone of their OVJP development—a seven-layer, 80 pixels-per-inch (PPI), green, “commercial-level” phosphorescent array on a 6-inch substrate that provides “comparable device performance as OLEDs deposited by vacuum thermal evaporation (VTE).” The exhibition, UDC’s business conference presentation, and discussions with employees at its booth revealed more information about the technology. 

OVJP process

OVJP is based on a process that can be simply explained in a few key steps as follows:

• Organic materials are heated and vaporized in a crucible.
• An inert carrier gas transfers the organic material vapor to a microelectromechanical systems (MEMS)-based nozzle array.
• Lines of the material are patterned onto the substrate through the heated MEMS heads in a vacuum chamber.
• Continuous evacuation at each subpixel nozzle prevents residue adhesion, particles, and nozzle blocking.
• Layered material stacks are sequentially printed on a moving substrate by connecting the heads to multiple source lines for each color stack.  

OVJP equipment and advantages

The width and other print parameters are dictated by the MEMS nozzle design. The print heads control the direction of the vapor as well as define the line shape and sharpness. Head design is an important parameter in eliminating crosstalk or color mixing between subpixels. New nozzle heads must be fabricated for every panel with varying pixel designs. This implies some downtime is required to replace and calibrate new heads. The heads also likely have a usable lifetime limit, though no information is currently available on how long that might be. 

Similarly, conventional fine metal mask (FMM) pixel patterning requires individual mask design, fabrication, and downtime to replace and recalibrate the machine. FMMs also suffer from the requirement of frequent cleaning and a relatively short lifetime before they need to be scrapped. 

Although the concept seems simple, the implementation of OVJP surely is very challenging and has required a huge amount of new equipment design and innovative engineering. In 2020, UDC set up OVJP Corporation in Santa Clara, California, managed by a team of highly experienced engineers with long careers in display equipment design and manufacturing to manage the equipment and process development.  

Reported advantages of OVJP include the following:

• High material deposition flexibility, including subpixel control of the host, dopant ratio, and other emission stack materials
• High pixel aperture ratio; 30% aperture ratio is already possible, and up to 50% may be feasible
• High material utilization
• No FMM or photomasks; unique MEMS arrays are required for every panel design but can be made at a reportedly relatively low cost and potentially have long lifetimes
• Clean process that enables printing of a wide variety of materials in a single chamber
• Scalability to large substrates, including Gen 10.5
• No material degrading solvents are used in the vapor transfer or printing
• High throughput, small footprint, and highly competitive capital costs

The OVJP pilot system has successfully printed 80 PPI patterns, which is equivalent to the resolution of a 4K 55-inch panel. One hundred sixty PPI compatibility, the resolution of a 24.5-inch 4K panel, is in development and should be feasible soon. UDC believes that in the future, even higher resolutions may be achieved. This implies that OVJP already offers sufficient precision to pattern TV panels, that monitors will also likely easily fall within its application range, and that even notebook panels may be possible in the longer run. Only smartphones and high-resolution tablets might be beyond OVJP’s capability. 

Comparison to other OLED patterning techniques

In theory, OVJP offers many of the same benefits as fine photo mask (FPM), that is, using photolithography to pattern RGB subpixels. Japan Display Inc. (JDI) refers to FPM as “eLEAP,” and Visionox calls it “ViP,” which is garnering intense interest these days. Both OVJP and FPM are “FMM-less” technologies. Because the FMM-based VTE process is so expensive to scale to larger substrates, and many of its inefficiencies are exacerbated on larger panels, the industry is keen to develop alternatives that can offer similar performance at lower cost. 

UDC has demonstrated similar efficiency, voltage, and lifetime results between OVJP and conventionally evaporated OLED materials (see Figure 2).

There are almost always trade-offs in technological choices, with various approaches having their own advantages and disadvantages. In the case of fabricating RGB OLED subpixels side-by-side:

• FMM-based VTE has the power of incumbency. It has many disadvantages, but FMM is the de facto industry standard because it is proven in mass production. Any competing technologies need to verify clearly better cost and performance to replace it.
• FPM promises significant efficiency, brightness, and lifetime improvements over FMM due to its ability to pattern very high pixel aperture ratios. Also, it is more scalable and flexible. Both JDI and Visionox have stated they will begin pilot production in 2024 and then ramp to high volumes from there. FPM may offer lower costs than FMM, but that is yet to be proven. It is a comparatively complicated process, and there are some concerns about yield rates and manufacturability.
• OVJP could overcome most of the issues related to both FMM and FPM and provide equivalent device performance, all at significantly lower capital costs. There are no OVJP equipment price estimates yet and individual machines will likely be very expensive. However, compared to the large number of process chambers required for FMM—and the many process steps in the case of FPM—the OVJP process is all contained in a single tool with only a few chambers. Also, OVJP material costs should be considerably lower than either FMM or FPM due to its high material utilization and potential to recycle unused material with relative efficiency. On the other hand, it is still too early to assess OVJP’s cost-benefit compared to WOLED and QD OLED, the two already established OLED TV technologies—which have lower costs than current RGB side-by-side OLEDs—that OVJP would initially target to displace. 

The future of OVJP

It is undeniable that OVJP presents an interesting approach to OLED patterning. However, its commercialization is still far off in the future. UDC has not announced any specific timeline for selling production equipment and has only given a rough estimate that commercialization is still three to five years away. Because UDC has such a strong and growing materials and technology business, the company does not need to rush the OVJP roadmap, which is a common problem for companies developing new and unique technological solutions. Developing major new display technologies is rarely a rapid process.

Theoretically, the potential of OVJP is promising, but only time will tell if it can live up to its promise. There certainly are bound to be many challenges that UDC and OVJP Corporation must overcome before the technology comes to market. But if it happens, OVJP offers the hope of significantly reducing costs while improving image quality, particularly for larger-size flat panel displays (FPDs). OVJP may even become a catalyst to finally expand large-size OLEDs from their current high-end niche segment to a mainstream FPD technology. 

To read more insights and analysis covering market trends and industry forecasts prepared by Omdia’s Display practice, click here.