Dr. Myungjong Kim of KIST, revealed in his presentation ‘Development of Customized Graphene Using CVD’
For OLED to become flexible, barrier is important, and customized synthesis of barrier is required.

With constant talk of foldable and bendable displays, why is the development of flexible displays so slow?

On the 17th, Dr. Myung-Jong Kim of the Korea Institute of Science and Technology (KIST) gave a presentation at the Flexible Display Technology Trends and Issues Seminar held at KINTEX in Ilsan. He said, “In the future, displays will be based on OLED and will become larger, more transparent, and flat.” He continued, “Large-area CVD graphene is applied in various fields, but since it is also used as a transparent electrode, it can also be utilized in flexible/transparent displays.”

He presented on the topic of 'Development of customized graphene using CVD that can be used in flexible displays', explaining how far the technology has been developed for graphene to be applied to displays and how it can be utilized.


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In general, the touch panel of a mobile phone uses an ITO (indium tin oxide) film. This ITO film has several problems. Currently, our country imports indium from China, but since indium is not a substance that is naturally produced on Earth, its supply will be limited over time. In addition, the process temperature is high and it is difficult to apply to flexible substrates. Various controls are required when handling ITO, and it breaks easily, and when applied to OLED, there are problems such as indium diffusing into the organic layer, so a transparent electrode material of another type is needed to complement the shortcomings of ITO.

When it is time to find a material to solve the ITO film problem

To replace ITO, it must be electrically conductive and have good mechanical strength. Alternative materials include carbon nanotubes (CNT), silver nanowires, metal meshes, conductive polymers, and graphene. Although these materials have been prototyped and are in the mass production stage, they are difficult to use as transparent electrodes due to problems such as permeability, area, rough surface, and haze.

Graphene is a suitable alternative when considering conductivity and mobility. Graphene is obtained through chemical exfoliation and used as a transparent electrode, but this is sufficient as an energy electrode, but it is difficult to use it in a display. As a new method of obtaining graphene is used, the epitaxial growth method, and it has been discovered that CVD graphene can be grown on nickel films. The application of this method has proven that a single sheet of graphene can be grown on copper foil, making the synthesis of CVD graphene easier.

Research has shown that graphene can be grown on 30-inch copper foil and transferred to the desired PET material to a form that can actually be used. Sony has developed a manufacturing technology that performs the entire process from graphene synthesis to transfer using a roll-to-roll process, and Hanwha Techwin has developed a film coated with graphene that is tens of inches long. Haesung DS has developed a technology to mass-produce large-area graphene measuring 34 inches.

Developing a new way to use graphene as a barrier

Dr. Kim Myeong-jong's research team came up with a method to use graphene as a barrier. A barrier is important for OLEDs to become flexible. Currently, glass is the best barrier. If other materials are used instead of glass, a barrier is needed to protect OLEDs, which are vulnerable to oxygen and moisture.

The idea the research team came up with was to divide the growth of CVD graphene into two stages, by adding less oxygen in the first stage and more oxygen in the second stage, taking advantage of the fact that the growth rate is fast at the beginning but slows down over time, and reduce the crystals. When the crystals were reduced and the water vapor permeability (WVTR) was measured, it was found that 60% of water vapor could be blocked at 0.5 nm.

The barrier must block not only moisture but also oxygen. When silver nano-wide or hybrid electrodes are made, Ag (silver) oxidizes easily, so durability is poor. This drawback can be overcome by using graphene, which acts as a barrier to oxygen and prevents the crystal from changing over time.

Dr. Kim Myeong-jong said, “Research is continuing to synthesize customized barriers using CVD graphene that can be used on a large area,” and “The price is also coming down to the level of ITO film, so commercialization of large-area graphene is imminent.”