[Reading Science] Korea's Display Industry in Crisis... Maintaining Ultra-Gap with New Technologies

Display Market Share Ranked No.1 in 2021
Low-End Segment Already Lost, High-End Still Leading
Focusing on Advanced Technologies Like Ultra-High Resolution, Large Size, and Flexible Displays

In modern digital society, displays are considered an essential technology, often referred to as the "second semiconductor." South Korea has consistently led the market since surpassing Japan in 2004 to become the world's number one display producer. However, its position is now being challenged by China's rapid advancement. In 2021, China took the top market share, and South Korea has effectively given up on low-cost liquid crystal displays (LCDs). While South Korea still dominates the premium organic light-emitting diode (OLED) market, China's pursuit is formidable. Experts advise actively developing new technologies such as ultra-high resolution and large-size displays, flexible devices, rollable and bendable displays to pioneer new markets. The government also launched a public-private consultative body last June to maintain a display technology gap. Let’s take a look at the current status of display technologies being developed in South Korea.

[Image source=Yonhap News]

Searching for New Material Displays.

Displays have evolved as the methods of producing light have improved. The first TV cathode ray tube (CRT) displays, made with electron guns and vacuum tubes, disappeared with the advent of flat-panel displays. Flat-panel displays are divided into plasma displays (PDP), which have phosphors inserted between glass plates, and LCDs that illuminate liquid crystals with backlights. Until recently, LED (light-emitting diode) displays using directly emitting diodes were widely used, but nowadays OLEDs using organic compounds dominate.

According to recent data released by the National Science and Technology Council (NST), South Korea is taking a step further by actively developing next-generation displays using perovskite optical materials and metamaterials. In June, the Korea Basic Science Institute (KBSI) developed technology to precisely control perovskite emitters. Perovskite refers to a mineral structure discovered in 1839 by Russian mineralogist Lev Perovski. Known as the ABC3 chemical composition, it generally refers to oxides where two types of cations each bond with three anions. It is characterized by excellent light absorption and outstanding optical and electrical properties. Due to its high luminous efficiency and color purity, it is attracting attention as a next-generation material to replace OLEDs. However, it had a critical drawback: ion bonds become unstable when exposed to heat or light, degrading display performance. The KBSI research team used time-resolved fluorescence lifetime imaging microscopy (FLIM) to analyze changes in the state of quantum particles and identified the causes that reduce emission stability. They also developed technology to effectively control ion bonding pathways using silver nanorod photonic crystal substrates.

There are also displays using metamaterials. The Korea Institute of Machinery and Materials (KIMM) recently developed a stretchable meta micro-LED display that does not distort images even when stretched or folded. This new technology solves the chronic problem of image distortion in rollable or foldable displays at the bending or folding points. The LED can be stretched by 25% without image distortion. The secret lies in the metamaterial. Metamaterials are human-made materials that can freely control interactions with light or matter through ultra-fine design. The metamaterial developed by the institute maintains its original proportions without shrinking vertically even when stretched horizontally.

Technology to solve the crease problem of the currently popular foldable smartphones has also been developed. The Korea Institute of Industrial Technology (KITECH) recently developed a fluorine-based polyimide optical film that does not form creases even after being folded and unfolded more than 200,000 times. It has durability that withstands folding and unfolding over 500 times a day for more than a year without any issues.

Flexible substrates are also essential

In next-generation displays emphasizing flexibility and portability, not only the "front" but also the invisible substrate is important. Substrates that do not wrinkle or break even when bent or curved are necessary. Inside displays, substrates composed of fine metal lines and semiconductors must exist. The Electronics and Telecommunications Research Institute (ETRI) developed stretchable inorganic semiconductor device technology in August last year that operates normally even when bent or stretched. Inspired by springs, they densely integrated high-performance oxide semiconductor transistors on a wavy horseshoe-shaped polyimide flexible substrate. When pulled, the wavy horseshoe shape straightens like a spring being stretched, maintaining the function of internal wires and semiconductor transistors. Compared to existing stretchable oxide semiconductor devices, it has 15 times higher directivity and twice the current driving performance.

South Korea is also ahead in developing display technology for metaverse (extended virtual worlds) that requires ultra-high resolution. On the 17th, a research team led by Professor Jo Himchan from the Department of Materials Science and Engineering at KAIST developed a patterning technology capable of producing augmented reality (AR) and virtual reality (VR) display panels with much higher ultra-high resolution than existing ones. Nanomaterials for solution processing, such as quantum dots and perovskite nanocrystals, which are attracting attention as next-generation emitters due to their high color purity and luminous efficiency, are difficult to produce uniform ultra-high resolution patterns while maintaining their excellent inherent optical properties.

The research team designed materials that facilitate crosslinking chemical reactions between nanocrystal ligands by utilizing the strong photocatalytic properties of quantum dots and perovskite nanocrystals. This allows the complete preservation of the intrinsic optical properties of luminescent nanomaterials. They successfully produced uniform ultra-high resolution (about 12,000 ppi) perovskite nanocrystal patterns with a pattern width of approximately 560 nanometers (nm). This ultra-high resolution far exceeds the displays commonly used in existing augmented and virtual reality (several thousand ppi).

Technology capable of reproducing the chameleon’s ever-changing skin colors and the beautiful feather colors of peacocks has also been developed. Last month, Dr. Pyo Jae-yeon and the smart 3D printing research team at the Korea Electrotechnology Research Institute (KERI) succeeded in implementing three-dimensional diffraction gratings that can control the path of light using their "nano 3D printing technology."

This new technology applies the principle of structural color observed in nature to advanced display technology. Dr. Pyo said, "This is a world-class 3D printing technology that can accurately implement desired structural colors at desired locations without restrictions on substrate material or shape," adding, "It can overcome the limitations of the standardized form-factor of display devices and bring diversification in shapes."

With these technological developments, South Korea is breaking the existing "paradigm" of display technology and countering China’s pursuit. An NST official stated, "Through the public-private consultative body, industry, academia, and research institutes related to displays are determined not only to maintain the current technological gap but also to make it impossible for latecomers to catch up," and added, "Recent technology development trends show that South Korea is developing world-first disruptive technologies one after another, changing the existing paradigm."