Professor Jang-Kun Song's research team from the Department of Display Engineering demonstrated a transparent OLED display capable of displaying different information in both directions by integrating a Yb-Ag transparent electrode with work function control properties and excellent surface characteristics, along with a novel pixel arrangement.

Transparent displays are one of the most advanced display technology fields in which South Korea leads globally. At last year’s CES exhibition in Las Vegas, LG Display’s transparent OLED was selected as the best product of CES. However, transparent displays have yet to secure a killer application and are currently applied only in niche markets.

The biggest advantage of transparent displays is their ability to provide information while maintaining a sense of spatial openness. Development of core technologies and application products that fully leverage this advantage is essential for expanding the transparent display market. For example, if a transparent display can provide different information to two people facing each other while not obstructing their view, it could play a crucial role in various environments such as education, meetings, consultations, and customer service.

To achieve this, advanced transparent electrode technology and a display pixel structure capable of displaying bidirectional information with a minimal increase of pixels are required. Professor Jang-Kun Song’s research team, including his master course student Eun-Young Choi, developed a Yb-Ag alloy electrode with high transparency, high conductivity, extremely low surface roughness, and work function tunability. They successfully demonstrated a transparent display incorporating this electrode. Additionally, they developed a technology that separates the areas with opaque TFTs from those without, enabling independent operation of single-directional and bidirectional information display pixels, allowing the display of different information in both directions.

The newly developed bidirectional transparent display technology can also adjust the relative brightness on both sides. Therefore, it can be used for a bidirectional transparent displays on a store window, where the ambient brighness inside the store is much different from that outside. This capability makes it a crucial technology for expanding the transparent display market.

This research was supported by Korea Institute for Advancement of Technology(KIAT) grant funded by the Korea Government(MOTIE) under  HRD Program for Display Industrial Innovation and by the Ministry of Education’s Basic Research Laboratory Program. The research findings were published in Light: Science & Applications (IF: 20).

※ Paper Title: Transparent OLED displays for selective bidirectional viewing using ZnO/Yb:Ag cathode with highly smooth and low-barrier surface

※ Journal: Light: Science & Applications

※ D.O.I: https://doi.org/10.1038/s41377-024-01739-0

▲ (Top)A transparent electrode with high transmittance and low surface roughness using a Yb:Ag alloy,
(Middle)Various display modes based on pixel arrangement and operation—front display mode, identical image display on both sides, and different image display on the front and back,
(Bottom) The driving circuit and image signal application method used to achieve these display functions