Researchers report stretchable quantum dot display with 53,300-nit brightness

A research team led by Professor Jiwoong Yang of the Department of Energy Science and Engineering at DGIST reported developing a stretchable quantum dot display (QLED) that keeps sharp image quality while stretching, according to Phys.org. The findings were published in Nature Nanotechnology. The work was carried out with teams led by Professor Moon Kee Choi of UNIST and associate director Dae-Hyeong Kim of the Institute for Basic Science (IBS) Center for Nanoparticle Research, Phys.org reported. Phys.org reported the researchers described the technology as the world's first foundational technology for an ultrahigh-resolution stretchable QLED.

According to Phys.org, conventional stretchable-display technologies stretch only the wires, called interconnects, while the light-emitting regions stay unchanged. The report stated that the share of the display area that emits light therefore drops as the display stretches, lowering image quality. Researchers have been working on light-emitting devices with 'intrinsic stretchability', in which the pixels themselves stretch like rubber bands, the report said. However, patterning soft, rubber-like layers into fine, high-resolution pixels has proven extremely challenging, and conventional organic composite materials have suffered from reduced color reproduction and brightness, according to the report.

The team developed a fabrication process called LIFT for ultrahigh-resolution stretchable QLEDs, according to Phys.org. The process chemically bonds quantum dots — light-emitting nanoparticles — with an elastic polymer that stretches like rubber, then transfers fine patterns onto a surface like stamping a seal. The team also applied a treatment to the surface of the light-emitting layer to improve its electrical conductivity and adhesion, the report said.

Using this process, the team created patterns with a pixel density of up to 16,000 pixels per inch and produced multicolor pixels using stretchable red, green and blue light-emitting layers, according to Phys.org. The device reached a maximum brightness of 53,300 nits, which the report compared with a previous limit of 15,000 nits or less for stretchable light-emitting devices. Phys.org described that brightness as the highest level reported for stretchable devices.

The device also operated stably without mechanical damage or image-quality degradation when stretched to approximately 65% beyond its original length, according to the report. Yang said the study was significant because the team achieved fine pixel fabrication and improved light-emitting performance by controlling surfaces and interfaces while maintaining the stretchability of the quantum dot composites.