Making Flexible OLED Displays

Organic light-emitting diodes (OLEDs) are supposedly the next big thing in display technology.

In fact, over the years, several display makers have spent billions of dollars to build new and large OLED fabs. To be sure, OLEDs enable brighter displays, as compared to traditional LCD technology. OLEDs use a series of thin, light-emitting films, which enables the display to produce brighter light.

OLEDs come in two forms–rigid and flexible. In fact, OLEDs promise to enable the long-awaited flexible display, which comes in foldable, rollable and stretchable forms.

So far, though, OLEDs have only fulfilled some of their promises. OLEDs have yet to take off for large-screen TVs, as the manufacturing flow for the technology is complex and difficult. And LCD TVs, the competing technology, are cheap and relatively easy to make.

But OLEDs are making inroads for small-screen devices, at the expense of the traditional technology–LCDs. “OLEDs are seeing market success for smartphones,” said Max McDaniel, director and chief marketing officer for the Display Business Group at Applied Materials.

In fact, OLEDs are also catching on for both smartphones and smartwatches. Apple, LG and Samsung have jumped on the OLED display bandwagon, at least for some products. And Chinese OEMs are also developing a range of devices using OLED displays.

Still, there are challenges in the OLED front. “OLED is a completely different device. You get rid of the backlight. And you now have a red, green and blue OLED material that is deposited on the glass. When you put current through it, it lights up all by itself,” McDaniel said. “The OLEDs themselves are vulnerable to contamination and temperature. They have a low-thermal budget. They can’t be exposed to any water or oxygen. And they can’t be exposed to the usual lithography steps.”

Looking to propel the next wave of OLED displays, Applied Materials has rolled out two new systems. The tools enable the volume production of OLED displays for both mobile products and TVs. The tools include the AKT-20K TFE PECVD and AKT-40K TFE PECVD. The AKT-20K is geared for 925- x 1,500-mm displays, while the AKT-40K is for 1,250- x 2,200-mm products.

Both tools deposit thin-film encapsulation barrier layers that are critical for protecting OLED devices. These high-performance films, deposited at low temperatures of <100°C, address the susceptibility of OLED material to degrade when exposed to environmental elements.

These systems allow display makers to replace the rigid insulating front glass on the devices. All told, the tools will help enable bendable and curved displays for a new generation of devices, according to James Xiao, vice president and general manager of the CVD & EPG Division within Applied’s AKT Display Business Group.

Flexible displays have been promised for years, but now the technology may finally take off. “Flexible OLED displays could be used in four types of form factors: bendable dynamic, foldable dynamic, fixed curved, and flat with a flexible substrate,” said Jennifer Colegrove, chief executive of Touch Display Research.

“We forecast that flexible OLED displays will have tremendous growth in the next several years,” Colegrove said. “Flat OLED displays with flexible substrate have been implemented in the Apple Watch because of the thin, lightweight characteristics. However, we forecast this form factor will decrease in the next several years, since it didn’t take advantage of the ‘curve’ characteristic of flexible OLED displays.”

Others have a different viewpoint. “Flexible OLED production yield has improved dramatically over the last few years, which could prompt panel manufacturers to ramp up flexible OLED production lines,” said Jerry Kang, principal analyst at IHS, in a recent report. “Market growth could also accelerate when flexible displays debut in foldable, rollable and stretchable forms.”

In fact, flexible displays are expected to comprise 15% of the total display market revenue in 2024, according to the research firm. As flexible OLED production continues to improve, revenue from flexible display production will expand at a compound annual growth rate of 44% from 2014, to reach $23 billion in 2024, according to IHS.

Flexible displays are feeding the market for various applications. For example, LG Electronics and Samsung have both applied flexible OLEDs to their flagship smartphones. The Apple Watch, which uses flexible display technology, has also added to the momentum of OLED in wearable devices. “Flexible display technology is not only gathering heated attention from electronics giants, but it is also stimulating startups to experiment with novel applications and innovations,” Kang said.