Researchers at DGIST's (President Kun-woo Lee) Department of Energy Science and Engineering, led by Professor Ji-woong Yang, in conjunction with Professor Moon-kee Choi of UNIST’s Department of New Materials and Dr. Taeg-hwan Hyun of the IBS Nanoparticle Research Center, have developed a double-layer dry transfer printing technology that simultaneously transfers layers that transfer electrons and light onto a substrate. Their work was published in Nature Photonics.
This technology is anticipated to significantly improve the immersive experience by offering a more lifelike image in both virtual reality (VR) and augmented reality (AR).
Recent advancements in wearable, mobile, and Internet of Things (IoT) technology drive demand for AR, VR, and wearable displays. Wearable displays for the eyes or wrists must display a lot of information on a small screen and have ultrahigh-quality patterning to prevent users from feeling lightheaded.
With its outstanding color purity and reproduction, quantum dot nanoparticles are emerging as the next generation of materials for display light emission. However, because of its poor luminescence efficiency—less than 5%—conventional dry transfer printing, which involves depositing quantum dot ink to a substrate, has not been employed for actual display manufacturing, despite being able to realize ultrahigh-definition pixels.
In this regard, DGIST Professor Ji-woong Yang, UNIST Professor Moon-kee Choi, and IBS Director Taeg-hwan Hyun worked together to create a method for dry transfer printing that can provide brilliant light even at low current levels. This makes high-resolution pixel patterning technology possible and produces ultrahigh-definition, highly effective light-emitting devices.
In fabricating light-emitting devices, the novel high-density double-layer thin films with reduced interfacial resistance enable electron injection and regulate leaky charge transport, resulting in high external quantum efficiency (EQE) of up to 23.3%. This is similar to quantum dot light-emitting systems' greatest theoretical efficiency.
The researchers confirmed the viability of mass manufacturing for product commercialization. They also employed the novel thin film to construct ultrahigh-definition patterns of quantum dots up to 25,526 PPI and reach an 8 cm × 8 cm area through repeated printing.
By using double-layer dry transfer printing technology to reduce interfacial resistance and facilitate electron injection, we have fabricated light-emitting devices that are simultaneously ultrahigh-definition and high efficiency. The light-emitting devices with double-layer thin films fabricated using this technology exhibited high EQE of up to 23.3%, similar to the maximum theoretical efficiency of quantum dot light-emitting devices, which is a very significant result.
Ji-Woong Yang, Professor, Daegu Gyeongbuk Institute of Science and Technology
Professor Moon-kee Choi from Ulsan National Institute of Science & Technology added, “We are pleased to have developed a technology that enables higher resolution screens in VR and AR through this research. Through further research, we will strive to broadly apply quantum dots with high color reproduction and color purity to smart wearable devices.”
The National Research Foundation of Korea and the Samsung Future Technology Development Program supported this study financially.
Journal Reference:
Yoo, J., et al. (2024) Highly efficient printed quantum dot light-emitting diodes through ultrahigh-definition double-layer transfer printing. Nature Photonics. doi.org/10.1038/s41566-024-01496-x.