Seoul National University's College of Engineering (Dean Byoungho Lee) announced on November 16 that a joint research team led by Professor Jeonghun Kwak of the Department of Electrical and Computer Engineering and Professor Jaehoon Lim of Sungkyunkwan University (First authors are Tae-Soo Lee and Byongjae Kim) has developed a quantum dot material and device structure that can be operated stably even under high luminance conditions and a ultra-bright red QLED that emits up to 3.3 million nits of light and operates stably even at high luminance of tens of thousands of nits.
 
Currently, the use of self-luminous QLED is limited to low- and medium-brightness (hundreds to thousands of nits) displays such as TVs, laptops, and mobile phones. In order for QLEDs to be used in various fields such as AR/VR devices, outdoor displays, and lighting and phototherapy devices, high-brightness conditions of tens of thousands of nits or more are required but QLED devices so far have not operated at high luminance or have shown very low device efficiency and stability.
 
In order to achieve high luminance, a high current must be applied to the QLED. However, it has been difficult to fabricate high-brightness QLEDs due to accelerated device degradation due to Joule heat generation caused by high current and reduced luminous efficiency of quantum dots due to the increase in non-emission Auger recombination due to the generation of multi-excitons.

The joint research team developed a material that can maintain luminous efficiency even at high currents by effectively suppressing non-luminescent Auger recombination that occurs at high currents by precisely controlling the structure of the shell constituting the quantum dots.
 
In addition, by using a silicon substrate, which has high thermal conductivity, deterioration of the device due to Joule heat was suppressed while the luminance was increased by optimizing the front light emitting structure to increase the light extraction efficiency. Finally, by controlling the number of quantum dots inside the emission layer, the formation of multi-excitons with low luminous efficiency was minimized.