OLED Will Advance from Smartphone to IT Products as Related Large-Generation Fabs Are Being Planned, but Evaporation Equipment Poses Challenges, Says TrendForce
TrendForce’s latest report—AMOLED Technology and Market Status—points out that the display panel industry has initiated plans for large-generation fabs that manufacture OLED panels. The migration of the OLED display technology to larger generations is driven by the recent improvements in related process technologies and materials. Also, brands have also been pushing for the adoption of OLED for larger display products. TrendForce forecasts that by 2025, the penetration rate of OLED panels among IT products will reach 2.8% on account of the gradual deployment of the supporting panel production capacity. Then, the OLED penetration rate in the IT segment is expected to take off noticeably in 2026, coming to 5.2%.
According to TrendForce’s analysis, panel suppliers are confronted with challenges in several areas as they plan to migrate OLED panel manufacturing from the existing G6 fabs to larger-generation fabs so that this display technology can cross into the IT segment. These areas are as follows:
[1] Evaporation Equipment
Regarding the selection of OLED evaporation equipment and related process technologies, some panel suppliers are hoping that the vertical evaporation method will solve the problem of the sagging of the fine metal mask (FMM). However, vertical evaporation is a new processing method that still has a lot of technical uncertainties to be worked through. As for the existing horizontal evaporation method, panel suppliers want to see further optimizations so that they can maintain a certain level of production capacity with less number of equipment than before. Additionally, Apple is thinking about adopting the two-stacked tandem structure (Tandem OLED) that can significantly increase the lifespan of its OLED displays. From panel suppliers’ perspective, setting up evaporation processing capacity within a certain amount of fab space is a lot harder if OLED panels feature the tandem structure. However, there are alternative solutions for increasing the lifespan of OLED displays. One way is to perform an OLED pixel simulation, through which a blue subpixel layer is added to help achieve a better color balance and longer lasting colors.
Raising glass utilization rate is also another aim behind the migration to larger-generation fabs. For instance, G8.7 currently has about a 10% gain in production efficiency compared with G8.5. Nevertheless, target customers may have a preferred supplier for the evaporation equipment. In the case of Apple, it favors Cannon Tokki from Japan. Hence, there is a possibility that the sizes of OLED panel substrates could be limited by the panel sizes that Tokki’s evaporation equipment can handle in the future.
Turning to the technologies in the manufacturing of OLED panel backplanes, LTPO offers a higher efficiency in terms of power consumption. Additionally, large-sized OLED panels will need an auxiliary electrode to support the existing transparent cathode in the pixel circuit. The auxiliary electrode helps boost conductivity and thereby resolve the problem of IR drop that is often seen in large-sized panels. On the other hand, the number of photo masks used in fabricating a pixel circuit is determined by the locations of electrodes, so certain designs may require more masks. Moreover, adding a new electrode could affect the transparency of OLED panels.
[2] Foldability
If OLED is to be adopted for foldable notebook computers, finding the right kind of material for the cover lens also requires some considerations. Currently, ultra-thin glass (UTG) is superior to colorless polyimide (CPI) in terms of performance. However, the former has shortcomings such as a higher price and a supply chain that is relatively less developed. Samsung has adopted “Color Filter on Encapsulation (COE)” for the OLED displays of its foldable smartphones. This solution reduces the thickness of an OLED display by eliminating circular polarizer, thus allowing for higher brightness and greater foldability. As for foldable notebook computers, these devices have a larger screen size and thus susceptible to more glare. Therefore, to effectively absorb reflected light while abandoning circular polarizer, some kind of a “black pixel define layer (BPDL)” is needed in addition to the black matrix resist that is incorporated into the existing color filter. However, there are challenges in the manufacturing of a BPDL because a relatively thick film that is darkened with an organic dye is difficult to form and deposit using the exposure process.
[3] Touch Function
Looking at the touch function that is standard with smartphone display panels, it is more susceptible to environmental noise interference as the display size increase. In the past, mutual capacitance sensing was sufficient performance-wise. However, with OLED now being adopted for notebook computers that has a touch display, making the switch to self-capacitance sensing may be necessary in order to resolve the problem of false touch points. However, this change in sensing technology will also entail a review of the touch circuit design and the die sizes of the touch and display driver ICs so that the thickness of the bottom display border will not increase on account of the whole fan-out area.
[4] Image Sticking
At the system level, image sticking (burn-in) on an OLED display tends to occur in parts of the screen where app icons are located since icons are static images with fixed locations. This problem, which has to do with the aging of OLED pixels, has been continuously worked on since it first appeared. Anti-aging solutions now include pixel shifting and the tandem structure, which can reduce pixel current by half. In the future, the development of OLED could reach the point where burn-in could be effectively resolved. By then, a dark mode featuring a black background and white texts could also be possible for OLED displays.
Following the overview of the above-mentioned issues in the manufacturing of large OLED panels, TrendForce now turns to the adoption of OLED for IT products. On the whole, there are three main directions in technology development over the long run.
[1] Cost Reduction
Cost savings can be achieved through several ways such as raising glass utilization rate, streamlining the LTPO+COE process, optimizing the electron transport layer (ETL), developing local sources of the key materials, and adopting more advanced evaporation equipment. The cost of manufacturing large-sized OLED panels for IT products will also fall on account of other factors. For instance, the price of UTG will go down as the number of suppliers for this kind of material rises. Moreover, better choices could appear for the designs and materials of foldable notebook display hinges. Lastly, printing process has the highest material utilization rate. Therefore, panel suppliers will need to find ways to apply the printing process to the fabrication of the tandem structure and other parts of the OLED panel.
[2] Improvements in Efficiency and Reliability
Panel suppliers will be incorporating new technologies such as COE and micro-lens panel (MLP) to raise light-emitting efficiency and lower power consumption. At the same time, they will attempt to extend the lifespan of the existing OLED materials. To further minimize the problem of image sticking in certain parts of the screen, the user interface has to be designed in ways that address the issue of static image content causing OLED pixels to age and degrade.
[3] Greater Range of Applications
Flexible, thin, and self-emitting OLED panels enable different folding forms for various user scenarios. At the same time, they also allow for integration with other technologies such as under-display camera, fingerprint sensor, etc.
In sum, OLED is gradually becoming mainstream for smartphones, but it still has many challenges to overcome in order to expand into other applications that involve larger display sizes. Nevertheless, TFT-LCD as a traditional display technology is almost at its fullest maturity in terms of product design. Thus, OLED, which has a much larger room for imaginations, is a significant technology that brands will be focusing on in the future. TrendForce believes that the next one to two years will be a critical period for the growth of OLED in the market for IT products. The extent of the improvements in related technologies and the magnitude of investments in the supporting large-generation panel production capacity will determine if the adoption of OLED in the IT segment will proceed smoothly.
ABOUT THE AUTHOR
SP Chou has worked in the flat panel display industry for 17 years and has experience in the development and application of advanced technology from the practical end of manufacturing. With years of accumulated knowledge and experience, his current research focuses on the application trends of OLED and the evolution of related technologies, materials, and equipment, as well as the analysis of cost competitiveness.
