New blue quantum dot technology could lead to more energy-efficient displays

Quantum dot-based displays offer improved energy efficiency, brightness and color purity compared to earlier generations of displays. A revolutionary approach based on self-assembling chemical structures provides a drug. The production and analysis of these innovative blue quantum dots require state-of-the-art imaging methodology.

Although QD-LED displays are now available, the technology is still in its early stages and the available models have several drawbacks, particularly their blue subpixels. The most significant blue subpixels are those of the three primary colors. Down-conversion is the process by which blue light is converted into green and red light. Therefore, blue quantum dots need more precisely tuned physical characteristics. This often means that manufacturing blue quantum dots is extremely difficult and expensive, and that the quality of these dots is critical for any display.

But now a group of scientists led by Professor Eiichi Nakamura of the Department of Chemistry at the University of Tokyo has a solution.

Professor Eiichi Nakamura of the Department of Chemistry at the University of Tokyo said, “Previous strategies for designing blue quantum dots were top-down, taking relatively large chemicals and putting them through a series of processes to refine them into something that works. Our strategy is bottom-up. We have built on our team’s knowledge of self-assembling chemistry to control molecules precisely as they form the structures we want. Think of it like building a house out of bricks instead of carving one out of stone. It’s much easier to be precise, design the way you want, and more efficient and cost-effective.”

But the blue quantum dot created by Nakamura’s team is unusual not just because of the way it was made; when exposed to UV radiation, it emits near-perfect blue light, in accordance with the BT.2020 international standard for evaluating color accuracy. This is because their point has a special chemical composition that combines both organic and inorganic substances, such as lead perovskite, malic acid, and olelamine. And they can be forced into the required shape, a cube of 64 lead atoms, four on each side, by self-organization.

The second challenge. Stills from the video captured using the “cinematic chemistry” of the blue quantum dot, including an illustration showing the atomic arrangement of the sample. ©2022 Nakamura et al.

Nakamura said, “Surprisingly, one of our biggest challenges was discovering that malic acid was a key piece of our chemical puzzle. It took over a year of methodically trying different things to find it. Perhaps less surprisingly, our other major challenge was to determine the structure of our blue quantum dot. At 2.4 nanometers, 190 times smaller than the wavelength of the blue light we wanted to create with it, the quantum dot structure cannot be imaged by conventional means. So we turned to an imaging tool pioneered by part of our team known as SMART-EM, or ‘cinematic chemistry’ as we like to call it.”

Because the blue quantum dot is also quite short-lived, although this was expected, and the team is now looking to improve its stability with the help of industrial collaboration.

Journal reference:

  1. Olivier JGL Chevalier, Takayuki Nakamuro, Wataru Sato, Satoru Miyashita, Takayuki Chiba, Junji Kido, Rui Shang and Eiichi Nakamura : 8 November 2022, DOI: 10.1021/jacs.2c08227.

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