The original technology for a quantum dot display that does not change image quality even when stretched like rubber has been developed.

The research team of Vice Director Kim Dae-hyung (Professor, Department of Chemical and Biological Engineering, Seoul National University) and Director Hyun Taek-hwan (Distinguished Professor, Department of Chemical and Biological Engineering, Seoul National University) of the Nanoparticle Research Group at the Institute for Basic Science (IBS, President Noh Do-young) announced on the 16th that they have succeeded in developing the world's highest-performance stretchable QLED (Quantum Dot Light-Emitting Diode) in collaboration with the teams of Professor Choi Moon-ki from UNIST and Professor Yang Ji-woong from DGIST.

Development is actively underway on new form factors (device shapes) beyond foldable and rollable.

The core of the form factor innovation is the stretchable display. The stretchable displays developed so far have a structure in which only the wiring section, excluding the light-emitting section, stretches when stretched. When stretched, the area ratio of the light-emitting section to the screen (fill factor) decreases, which reduces the image quality, and the mechanical reliability of the interface between the light-emitting section and the wiring section decreases.

To solve the problem of image quality degradation, it is essential to develop a light-emitting element with “intrinsic elasticity” in which both the wiring section and the light-emitting layer stretch when stretched. Previous studies on the development of intrinsically elastic light-emitting devices have utilized organic electronic composite materials as light-emitting materials.

On the other hand, organic electronic composite materials have limitations in that they do not reach commercial-level performance in terms of mobility and color reproducibility.

The IBS research team designed a new stretchable light-emitting layer that uses quantum dots as light-emitting materials. First, the research team created a solution that evenly mixed red (R), green (G), and blue (B) quantum dots, an elastic polymer (SEBS-g-MA), and a hole-transporting material.

Afterwards, this solution was made into a uniform light-emitting layer with a thickness of 40 nm using spin coating technology.

“Our research team also developed a new high-resolution patterning technology that can be applied to stretchable quantum dot light-emitting layers,” said joint first author Professor Dong-Chan Kim of Gachon University (former researcher at the IBS Center for Nanoparticle Research) and explained, “By combining light-emitting materials and patterning technology, we were able to complete a full-color stretchable QLED display device containing pixels for all three colors of RGB.”

The device manufactured by the research team had a maximum luminance (brightness) of 15,170 nits and an operating voltage of 6.2 V, demonstrating the best performance among the stretchable quantum dot light-emitting devices developed so far.

The device developed by researchers at Stanford University in the United States in 2022, which was reported to have the best existing performance, had a brightness of 7,450 nits and an operating voltage of 15 V. It has dramatically improved performance.

This device does not suffer mechanical damage or degradation of luminous performance even when subjected to lateral pulling forces.

Additionally, there was no significant change in the distance between quantum dots within the device even when the distance was increased by up to 1.5 times.

For example, if you make a 20-inch QLED TV with this device, it can maintain the same light-emitting performance even if it is stretched to a 30-inch size.

“The key to this study is that we have implemented a device that does not lose performance even when stretched, while taking advantage of the high resolution and color reproducibility of quantum dot light-emitting devices,” said co-corresponding author Professor Choi Moon-ki of UNIST (former researcher at the IBS Center for Nanoparticle Research). “We plan to conduct follow-up research to optimize performance, such as increasing brightness and lowering operating voltage.”

“Shape-variable displays using stretchable elements are a key trend in the development of next-generation displays,” said Vice President Kim Dae-hyung, who led the research. “The technology developed by our research team can be applied to areas that are difficult to implement with flexible or foldable form factors, such as curved displays inside automobiles, and will be able to bring forward the era of free-form displays.”

The research results were published on April 15 (Korean time) in the online edition of 'Nature Electronics (IF 34.3),' a world-renowned journal in the field of electrical and electronic engineering.