Seoul National University College of Engineering announced that a research team led by Prof. Yongtaek Hong from the Department of Electrical and Computer Engineering has developed a high-performance transparent organic light-emitting diode (OLED) incorporating highly conductive transparent metal mesh top electrodes fabricated using a selective metal deposition technique.
Transparent OLEDs have attracted significant attention for next-generation applications including advanced displays, augmented reality (AR), automotive displays, and smart windows due to their capability for bidirectional light emission. However, despite achieving high optical transparency and excellent electrical performance, conventional transparent electrodes often face limitations when directly integrated onto OLED devices because their fabrication processes can chemically or physically damage the underlying organic layers.
To address this challenge, the research team developed a metal patterning technology based on a high-resolution transfer-printing process utilizing a metal-vapor-desorption layer (MVDL). This approach enables the fabrication of highly conductive transparent metal mesh patterns with micrometer-scale resolution without requiring chemical washing or lift-off processes. As a result, high-quality vapor-deposited metal patterns can be directly formed on organic stacks while minimizing damage to the underlying organic device layers.
The fabricated metal mesh electrodes simultaneously achieved high optical transparency of 93-99% and low sheet resistance of 1.1-4.0 Ω/sq. In addition, the electrodes exhibited a figure of merit (defined as the ratio of electrical conductivity to optical conductivity) exceeding 10,000, representing one of the highest figure of merit values reported for sub-micrometer-thick transparent electrodes. The research team further demonstrated transparent OLEDs incorporating the metal mesh electrodes as top electrodes. The resulting devices exhibited excellent transparency and electroluminescent performance without degradation of the underlying organic layers, highlighting the potential of this technology for next-generation transparent display applications.
According to the research team, the proposed technology offers both process simplicity and scalability by enabling direct high-resolution patterning of metal electrodes through conventional vacuum thermal evaporation.
Prof. Yongtaek Hong highlighted the significance of the research, stating, "This study presents a new process strategy that simultaneously achieves the excellent electrical characteristics and transparency of high-performance metal electrodes while allowing direct micropattern formation on organic devices." He added, "We expect this technology to serve as a key electrode platform for transparent displays and flexible optoelectronic devices, as well as a core manufacturing technology for transparent top electrodes in emerging applications such as facial recognition panels."
This research was published in a recent paper in the international scientific journal, Materials Horizons, and was selected as the outside front cover image for this issue.
Meanwhile, the research was supported by the Commercialization Promotion Agency for R&D Outcomes funded by the Ministry of Science and ICT (MSIT), and the National Research Foundation of Korea (NRF) funded by the Korea government (MSIT), and the Basic Science Research Program through NRF funded by the Ministry of Education.
□ Introduction to the SNU College of Engineering
Seoul National University (SNU) founded in 1946 is the first national university in South Korea. The College of Engineering at SNU has worked tirelessly to achieve its goal of 'fostering leaders for global industry and society.' In 12 departments, 323 internationally recognized full-time professors lead the development of cutting-edge technology in South Korea and serving as a driving force for international development.
