According to the latest issue of Science Progress magazine, researchers from the Massachusetts Institute of Technology and Samsung Advanced Technology Research Institute have developed a simple and easy to scale resin packaging technology that can increase the lifespan of quantum dot light-emitting diodes (QD-LEDs), especially blue light devices, by more than 5000 times. The study also revealed the degradation mechanism of QD-LED, providing new ideas for improving device stability and promoting the commercialization of this high-performance display technology. In the future, QD-LED using this packaging technology can be applied to flat screen TVs, AR/VR headsets, smartphones, medical imaging devices, and large-area lighting systems, presenting richer and brighter colors.
Quantum dots are nanoscale semiconductor materials that can emit pure colored light. QD-LED uses current to directly excite quantum dots to emit light. Compared with existing quantum dot display technologies, it has a simpler structure and higher efficiency. The biggest bottleneck hindering the commercialization of QD-LED is the short lifespan of blue devices. The stability of blue devices is only 1/50 to 1/100 of that of red and green devices, making it difficult to meet the long-term usage requirements of commercial display devices.
To identify the cause, the research team has developed a novel sampling technique that involves cutting tiny QD-LED devices into nanoscale ultra-thin slices and observing changes in the internal structure of the devices before and after operation using a high-resolution electron microscope.
As a result, it was found that during continuous operation, the three key functional materials responsible for luminescence inside the blue QD-LED would degrade, not only thinning in thickness but also changing in morphology. The originally separated quantum dots gradually merged and lost their original shape. This process is accompanied by the release of additional hydrogen and oxygen elements, which may be important factors leading to device degradation.
Based on this discovery, the team encapsulated QD-LED using an acrylic resin. The experimental results show that this layer of resin can effectively suppress the release of hydrogen and oxygen, slow down the structural changes of the internal material layer of the device, and significantly improve the stability of the device. Among them, the lifespan of red QD-LED has increased by about 8 times, while the most difficult to solve blue QD-LED has increased by more than 5000 times.
The research team speculates that resin encapsulation can prevent the formation of moisture around quantum dots, which is likely to be an important cause of rapid aging of the device. However, they also pointed out that resin encapsulation cannot completely eliminate all degradation mechanisms, so future plans will continue to optimize device structures and add new functional layers in QD-LEDs to further improve luminous efficiency and service life.