Looking Towards OLED’s FMM-Less Futures

The shift to reduce production costs and enhance the performance of OLED displays compared to traditional manufacturing methods that use fine metal masks (FMM) is creating an interesting dynamic in the display industry. There is a pressing need to address the limitations of existing vacuum thermal evaporation (VTE) equipment, which relies on FMM but is not suitable for large-scale display manufacturing due to its limitations in scalability and efficiency. Hence the interest when you hear thatSamsung Display recently acquired five of Orthogonal’s patents for FMM-less OLED manufacturing.

According to DSCC’s CEO, Ross Young, in his blog post, the approach developed by Orthogonal involves depositing the HIL/HTL and emitter layers by evaporation after forming the PDL, then delaying the evaporation of the second half of the stack (EIL/ETL/cathode) until all three colors are patterned. Orthogonal’s patents specify slot coating a fluorinated protection layer to shield the OLED layers before applying an “orthogonal” photoresist layer and using lithography to pattern the OLED layers. After completing the device, the ETL/EIL/cathode layers are evaporated, followed by a single encapsulation step, with three additional coating steps of the fluorinated protection layer to prevent damage from photoresist, oxygen, and water.

In contrast, the eLEAP/ViP approach by Japan Display and Visionox involves evaporating the entire OLED stack for each color before patterning and using CVD TFE for encapsulation after each color. This method also incorporates a rib structure to prevent dark spots by ensuring encapsulation layers are separated by color. Orthogonal’s method, if effectively implemented, could result in lower capital expenditures and product costs due to fewer encapsulation steps. Despite developing a three-color passive matrix prototype, Orthogonal faced challenges with damage to sub-pixels during multi-color patterning. Ross Young also suggests that Samsung Display’s acquisition of Orthogonal’s patents may indicate an effort to support and improve this approach, leverage it in negotiations with other developers, or block competitors from pursuing similar methodologies while wondering how the future will reveal Samsung’s strategic intentions with these acquired patents.

Orthogonal FMM-less OLED technology focuses on reducing both capital expenditures (CapEx) and overall product costs by eliminating the need for FMM, traditionally used in OLED production. This approach also enhances protection during manufacturing, potentially reducing defect rates and improving yield. Inkjet printing OLED technology is highly efficient in terms of material usage and offers flexibility in patterning, making it suitable for large-area OLED production. However, this technology faces challenges such as achieving uniform material deposition and maintaining high resolution and alignment precision. Overcoming these technical hurdles is essential for the widespread adoption of inkjet printing in OLED manufacturing.

Orthogonal, founded as a Cornell University spin-out in 2009 by Dr. John DeFranco, initially focused on developing photoresist chemistry based on fluorinated solvents for direct patterning of chemically sensitive materials, particularly organic electronics. Early interest in their technology came from large Taiwanese display companies working on OTFTs. However, due to limitations with FMM, Orthogonal pivoted to OLEDs in 2014. They later transitioned to organic photodetectors in 2018, aiming to help display suppliers provide more value with sensors produced on glass or plastic substrates. These organic photodetectors, known for being significantly more sensitive than CMOS sensors, could be made larger to enable multiple fingerprints.

During Display Week 2024, we covered the fact that TCL CSOT is set to initiate the production of OLED displays using inkjet printing technology in the second half of 2024, focusing on the IT and medical sectors. Proponents claim inkjet printed OLEDs offer significant advantages, such as higher aperture ratios, which lead to brighter displays, and superior lifetime performance, addressing key limitations of current OLED technologies. The technology facilitates the creation of transparent and flexible displays, broadening the potential applications beyond conventional screens to include innovative form factors and new device categories. The cost efficiency stems from better material utilization and reduced complexity in the manufacturing process.

Inkjet printing technology represents a significant advancement in OLED display manufacturing, with TCL CSOT leading this transition. By addressing cost and performance issues, this technology has the potential to transform the market, making OLED displays more accessible and versatile. The success of this transition will depend on overcoming challenges related to deposition uniformity and resolution precision.

FeatureOrthogonal FMM-less OLEDInkjet Printing OLEDUDC’s OVJP (Organic Vapor Jet Printing)
Deposition ProcessEvaporation of HIL/HTL and emitter layers followed by slot coating of fluorinated protection layer; lithography for patterning; evaporation of ETL/EIL/cathode layers after patterning​,Solution-based deposition using inkjet printers; direct printing of each layer,Heating and vaporizing organic materials, transferring vapor via inert carrier gas to MEMS-based nozzle array, patterning onto substrate​,
EncapsulationSingle encapsulation step after all layers are patterned; involves a fluorinated protection layer to prevent damage from photoresist, oxygen, and water​,Multiple encapsulation steps to protect each printed layer, increasing complexity and cost,Comparable to traditional VTE encapsulation, but benefits from potentially simpler and more integrated encapsulation steps due to direct patterning​,
Material ProtectionUses fluorinated protection layer and orthogonal photoresist to shield sensitive OLED layers from damage during patterning,Direct deposition reduces the need for additional protection layers but requires careful management of contamination and uniformity​,Continuous evacuation at each subpixel nozzle prevents residue adhesion, particles, and nozzle blocking, protecting the materials during patterning,
CostPotentially lower capex and production costs due to fewer encapsulation steps​,May have higher costs due to multiple encapsulation steps, but efficient material use can offset costs​,Potential for lower costs due to elimination of FMM and simpler patterning process, although new equipment design and nozzle head replacement could introduce costs,
Resolution and PrecisionSuitable for high-resolution displays by avoiding FMM limitations,Capable of high precision patterning, suitable for large-area OLED panels​,High precision and fine line sharpness due to MEMS nozzle design, capable of achieving high-resolution displays comparable to VTE-based OLEDs​,

Universal Display Corporation (UDC) has developed Organic Vapor Jet Printing (OVJP), its own advanced OLED manufacturing technology designed to eliminate the use of FMMs. The OVJP process involves heating and vaporizing organic materials in a crucible, then transferring the vapor through an inert carrier gas to a MEMS-based nozzle array. The materials are then patterned onto a substrate in a vacuum chamber, with continuous evacuation at each subpixel nozzle to prevent residue adhesion and blocking. Layered material stacks are printed sequentially on a moving substrate, with heads connected to multiple source lines for each color stack.

The MEMS nozzle design controls the direction and sharpness of the vapor lines, preventing crosstalk or color mixing between subpixels. However, new nozzle heads must be fabricated and calibrated for each panel design, requiring some downtime. This method eliminates the frequent cleaning and short lifespan issues associated with FMM, offering potentially lower capital expenditure and production costs due to fewer encapsulation steps and simplified manufacturing processes.

During Display Week 2023, UDC showcased a seven-layer, 80 PPI green phosphorescent array on a 6-inch substrate, demonstrating comparable performance to OLEDs deposited by vacuum thermal evaporation (VTE).

OVJP can manufacture high-performance OLED structures and architectures that are not feasible with the VTE method, using the same phosphorescent OLED (PHOLED) materials from UDC with similar performance in terms of efficiency and lifespan. UDC has already introduced the world’s first PHOLED stack printing with high-resolution RGB arranged side by side, achieving performance comparable to VTE. The goal of OVJP is to create a fast, space-constrained, and cost-effective OLED TV manufacturing platform.

I don’t personally believe that Samsung Display’s acquisition of Orthogonal’s patents is defensive or going to be used to fend off competition. As we can see, there are alternative FMM-less technologies that promise to do much the same, and there is a body of research that supports new approaches to materials and manufacturing techniques for OLED.

The real question is whether OLED manufacturing has the runway to make itself competitive on price in larger area displays, such as TVs, where the cost differential with older technologies, that continue to evolve and get better, is too much for consumers. It may also be that companies like TCL CSOT, all-in on inkjet printing, are suggesting that the opportunities for most cost-effective OLED manufacturing are more accessible than imagined meaning that Samsung Display may lock up developments in one area, but can’t really stop the evolving landscape of competing manufacturing technologies from taking shape and limiting any IP spoiling tactics.

If anything, the emergence of FMM-less OLED manufacturing techniques will favor Chinese companies competing against Samsung and LG, giving them the opportunity to close the technology gap quicker than the South Koreans may have anticipated. There are plenty of rumblings in the South Korean press about the extent of Chinese government support and spending on its display industry, with each week creating more hand-wringing and requests for South Korean government support from the local industry.