Special Issue _____ Development of OLED Display with Graphene Transparent Electrodes
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Innovative Combination of Dream Display and Next-generation New Material
Innovation Continues
OLED displays are considered the best displays after LCD since they have all the elements necessary to be a future-oriented display, such as ultrathin shape and high resolution. ETRI has recently developed an innovative next-generation display by combining OLED technology and graphene technology, which emerged as a new material for the future.
The next-generation OLED display used graphene for transparent electrodes, instead of using ITO (indium tin oxide). The size was also innovated: the display substrate became available in the world’s largest size of 370mm x 470mm, equivalent to the size of a 19-inch monitor, and the graphene electrode is only as thick as 5nm. In addition, since the display can be made flexible, OLED has potential to be used for producing wearable devices requiring high flexibility.
To Develop Unbreakable and Flexible Display
Many R&D participants and the technology industry have endeavored to develop flexible OLED displays for the future. To this end, improvement was made at a fast pace with regard to the core materials and structural technology, encompassing a flexible plastic substrate to replace a glass substrate, luminous pixels, and a transistor working as a switch.
Graphene was first discovered in 2004 as the next-generation electrode material and started to receive widespread attention in a decade ago. It was then proved to be an innovative material through academic research, with outstanding physical strength, electric conductivity, and flexibility. In 2010, researchers working in a related field were awarded the Nobel Prize in Physics.
Although graphene demonstrates outstanding electrical and optical performance at the level of a single layer, it had been difficult to directly apply it industrially due to process limitations. The most notable restrictions were even quality over a large area of a graphene thin film; transfer technology for OLEDs; and stable graphene patterning technology to create pixels in OLEDs. In addition, the thickness of 0.34nm, or 1/330,000 that of hair, had been a huge obstacle to proceed with a large-scale process.
Due to the damage to graphene in the process of transfer to the final substrate and the residue on the surface during process, technological development had been insufficient to produce OLEDs with graphene transparent electrodes.
Becoming a Global Display Powerhouse
ETRI researchers used graphene as a replacement of ITO, which has been widely used for transparent electrodes of OLEDs. Since graphene is flexible, it can overcome the mechanical weakness of ITO, which is susceptible to external impact.
In partnership with Hanwha Techwin, ETRI developed technology to grow large-size graphene and large-area transfer technology. In particular, the researchers significantly reduced transfer defects and residue, thereby achieving a technological leap forward to satisfy the specifications required for OLED transparent electrodes.
More specifically, the new technology can process graphene transparent electrodes with sheet resistance of 60Ω/m² applicable to OLEDs and at least 85% transparency. ETRI also became the first in the world to develop a fine patterning process, which is a prerequisite for display processes.
In Graphene 2017, the world’s largest conference to discuss graphene, in Spain, ETRI presented related papers and demonstrated its outcomes with great success.
Within the next two years, ETRI plans to partner with LG Display to develop electrodes made with graphene to apply to flexible displays as well as a coating technology to prevent the penetration of moist and air.
