A recent article in the IEEE Journal of Selected Topics in Quantum Electronics (JSTQE) discusses an exciting development in next-generation display technology. The research titled “Bright, Flexible, and Waterproof Top-Emitting InP Quantum Dot Light-Emitting Diodes on Al Foil” shows flexible and waterproof quantum-dot (QD) light-emitting diodes (QLEDs) that are very bright, with a record-breaking maximum luminance of 40,000 cd/m2. The research was conducted by Dr. Taesoo Lee, Dr. Geun Woo Baek, and Prof. Jeonghun Kwak at Seoul National University (SNU) in South Korea. These researchers are renowned experts in the field of electrically-driven QLEDs, and their innovative ideas are brightening the future of QD-based flexible and wearable displays. Let’s delve into their recent research in detail.
In 2023, the Nobel Prize in Chemistry was awarded to three scientists for their development of QDs, underscoring their significance for future display technology. QDs are one of the most promising emitters for display devices due to their excellent optical characteristics, including vivid color and bright light emission. Thanks to meticulous device design and improved QD materials, QLED technology is expected to be used soon in common display applications like TVs, making screen quality and vividness much better than other existing technologies. However, to extend the use of QLEDs to wearable devices or augmented reality (AR)/virtual reality (VR) displays, advancements in brightness and form factors are needed.
In this context, Prof. Kwak and his team explore new methods to create QLEDs that are exceptionally bright, flexible, and waterproof. They propose a “top-emitting” device architecture, where the light emits from the top of the device. This design allows for more flexibility in the choice of substrate for the QLEDs, even when the substrate is non-transparent. In the traditional “bottom-emitting” device design, we should select transparent materials like plastic or organic films for the flexible substrates because the light is emitted towards the bottom. However, these materials don’t conduct heat well, making it difficult to manage the heat generated at high brightness levels. To overcome this, Prof. Kwak’s team uses top-emitting structure and demonstrates that QLEDs can be fabricated on heat-dissipating aluminum foil, making them both bright and flexible. The luminance achieved in this work is the highest among reported values for flexible non-toxic QLEDs, attributed to reduced thermal degradation due to effective heat dissipation ability of metal foil substrate. Additionally, by adding very thin protective layers on top, they show that these QLEDs perform well even in wet conditions. The team believes this research will help usher in the era of next-generation flexible and wearable displays.
This research was conducted at the Inter-university Semiconductor Research Center at SNU, equipped with advanced tools for creating sophisticated semiconductor devices. Prof. Kwak oversees the “Advanced Opto & Nano Electronics (AONE) Laboratoy,” which specializes in various types of display technology, including QLEDs (more information can be found at https://aone.snu.ac.kr). He confidently asserts that the future of QLED technology is very promising, thanks to the hard work of researchers in both the display industry and academia. Dr. Lee, a post-doctoral researcher, is deeply investigating the microcavity structure to control emission properties, while Dr. Baek specializes in enabling various applications using QLEDs. The collaborative efforts of these scientists, each with their unique research focus, have resulted in significant academic and industrial achievements. For example, they worked together on combining the top-emitting front panel and backplane devices, and on careful design of the electrode patterns to display letters and symbols. The team continuously seeks innovative ways to apply QLED technology in next-generation optoelectronic applications, publishing creative and insightful research that propels the field forward.
Their latest article is available in the IEEE JSTQE, vol. 30, issue 3, Article No. 2000107 (DOI: 10.1109/JSTQE.2023.3323619). This article covers a wide range of research results, from device fabrication to detailed thermal simulations and practical demonstrations. It offers great insights into QLED technology and will inspire readers to explore the exciting world of QLEDs, contributing to the future of display technology. This work was funded by the Korea Government (MOTIE and MSIT) and Samsung Electronics Co. Ltd. and has been featured at 2024 International Meeting on Information Display (Korea) and International Conference on Display Technology (China) to encourage further studies in this area.
