April 23, 2024

The new issue of Science magazine provides an overview of nearly three decades of colloidal quantum dot research. It also assesses technological progress and the challenges in commercializing this promising technology, which has applications for everything from TVs to highly efficient solar collectors.

Thirty years ago, these structures were a scientific curiosity studied by a few enthusiasts. In the past few decades, quantum dots have been used in industrial applications, including various emerging and traditional technologies. Some of these materials have even made their way to commercial markets.

Los Alamos was the origin of many of the advances in Science, such as the first demonstrations of colloidal quantum dot lasing and carrier multiplication. They also pioneered research into quantum-dot light-emitting devices (LEDs), luminescent solar concentrators, and single-dot quant emitters.

Quantum dots can be controlled with high precision using modern colloidal chemistry. This allows them to have their properties, and therefore behavior, precisely controlled.

Several ongoing efforts have been made to exploit the size-controlled tuning of quantum dots’ emission colors and their high quantum yields, which are nearing the ideal limit of 100 percent. Quantum dots, color-converting phosphors, are used in screen displays and lighting technologies. Quant bubbles, with their narrowband emission and spectrally adjustable emission, allow for better color purity and more complete coverage of all color spaces than existing phosphor materials. Quantum dot TVs are one example of devices that have reached a mature technological level and are now available on the market.

Next up is the development of LEDs that are powered by quantum dots. The Science Review describes the various ways to implement these devices and discusses existing challenges. Quantum LEDs already achieve impressive brightness and near-ideal efficiencies close to the theoretically defined limit. This progress is mainly due to the continued advances in understanding performance-limiting factors, such as nonradiative Auer recombination.

This article also discusses the current status and challenges for solution-processable Quantum Dot Lasers.

Klimov stated that “making these lasers accessible would benefit a wide range of technologies including integrated photonics circuits, optical communications, lab-on a-chip platforms and wearable devices as well as medical diagnostics.”

Researchers at Los Alamos have made essential contributions to this field, including the discovery of mechanisms of light amplification within colloidal nanostructures as well as the first demonstrations of the lasing effect.

Klimov stated that the current primary challenge is demonstrating lasing using electrical pumping. Los Alamos is responsible for several milestones in the journey to this goal, including realizing optical gain through electrical excitation.

Quantum dots have also shown great promise in light-sensing and solar harvesting. They can be tuned to target specific wavelengths due to their tunable bandgap. This is particularly attractive when realizing low-cost photodetectors in the infrared spectrum. Colloidal quantum dots are used in solar energy technologies as an active element of solar cells and luminescent sun collectors.

The quantum dot technique could create a new generation of low-cost thin-film PV devices in photovoltaics using scalable solutions-based processing techniques like roll-by-roll. They could also enable new photoconversion schemes derived from unique physical processes of ultrasmall, “quantum-confined,” colloidal particles. A carrier multiplication process generates multiple pairs of electron holes from a single photon. Researchers at Los Alamos first described this process in 2004. Since then, intensive research has focused on its application in solar photochemistry and PVs.

Klimov added that quantum dot solar concentrators, or LSCs, are another promising field. The LSC technology can be used to convert windows and wall sidings. This could be used with solar panels on the roof to provide clean energy for an entire building. The LSC concept has been around since the 1970s, but it flourished only in recent years due to the introduction of specially-engineered quantum dots.”

Researchers at Los Alamos have made many contributions to the LSC area, including developing practical solutions for the self-absorption of light and high-efficiency devices with bi-layers (tandems). UbiQD Inc. is one of several start-ups actively working to commercialize a quantum-dot LSC.

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