Quantum Dot Researchers Win Nobel Prize For Bringing Color to Nanotech
The 2023 Nobel Prize in Chemistry goes to three scientists whose quantum dot research has made display and lighting technology more colorful.
The Royal Swedish Academy of Sciences has awarded the 2023 Nobel Prize in Chemistry to Moungi G. Bawendi (Massachusetts Institute of Technology), Louis E. Brus (Columbia University), and Alexei I. Ekimov (Nanocrystals Technology in New York) for their nanotechnology research. Each scientist played a pivotal role in the discovery and synthesis of quantum dot technology for devices ranging from LED lamps to television screens.
The research of the three scientists showed the impacts of reducing nanoparticle size, allowing designers to create different colors of light from the same materials. Image used courtesy of the Royal Swedish Academy of Sciences
This article gives a brief history of quantum dots and details the background of the three Nobel laureates whose research gives physicists today a new way to produce colored light.
Optics and the Bandgap: A Core Principle of the Research
Engineering students learn about the concept of bandgap when first learning semiconductor physics. The bandgap represents the amount of energy required for an electron to move to the conductance band where they may freely move between atoms.
This bandgap has been used to create more efficient semiconductors, LEDs, and voltage references. As the size of the material shrinks, the bandgap itself starts to change.
As the size of quantum dots shrinks, electron transitions require more energy, resulting in bluer light. Image used courtesy of Frontiers in Materials
Larger nanoparticles shrink the bandgap, causing redder light to be reemitted after absorbing a high-energy photon. Conversely, as the particle becomes smaller, electrons moving between bands release more energy, causing the reemitted light to move toward the bluer end of the spectrum.
This allows designers to control the color of light produced by a material without changing the chemical composition, opening the door for improved displays and optics technology.
Three Scientists' Findings Converge
The counterintuitive effects of nanoparticle size on color have been observed for hundreds of years. For instance, glass makers understand that certain conditions during the production process change the color of the resulting glass, even if the same materials are used.
In 1981, Alexei Ekimov published illuminating results on how he produced glass in his lab. He showed that factors such as temperature and heating time could profoundly affect the final color of the glass, even if the same ingredients were used. No stranger to quantum effects, Ekimov realized that he was observing the impacts of quantum mechanics.
To produce quantum dots of a distinct size, Moungi Bawendi used temperature control along with a carefully chosen solvent to regulate the size of quantum dots with high precision. Image used courtesy of the Royal Swedish Academy of Sciences
In 1983, Louis Brus, unaware of Ekimov’s publication due to the inability to access Soviet scientific journals, noticed that leaving a solution on a lab bench for some time caused the optical properties to change. He guessed that it was due to the particles growing, and, after synthesizing a fresh solution, verified his hypothesis and demonstrated quantum dot effects in a solution.
These discoveries, while impactful in their own right, are of little use to engineers without a way to tightly control the size of the dots. Moungi Bawendi discovered how to grow quantum dots of a precise size using a carefully heated solvent, allowing engineers to access distinct quantum effects.
Interacting With the Nano-World
While the impact of quantum effects in nanoparticles was initially believed to have no practical use, today’s engineers have grown comfortable with designing devices on the nanometer scale. With this acceptance, quantum dots are increasingly used in display technology, with more advancements on the horizon.
Thanks to the advancements of countless physicists and engineers, designers can now precisely control particles that have the same size relationship to a soccer ball as a soccer ball has to the Earth. Image used courtesy of the Royal Swedish Academy of Sciences
As microdisplays for AR and HCI become more common, device makers are turning to quantum dots to achieve smaller and higher-resolution displays. As is the relationship between scientists and engineers, now that science has shown we can precisely control nanoparticles for advanced applications, it is up to the engineers to create the technology that will drive the lighting and display industries.