Decades of research brings quantum dots to brink of widespread use


Date:
August 5, 2021
Source:
DOE/Los Alamos National Laboratory
Summary:
A new article gives an overview of almost three decades of research
into colloidal quantum dots, assesses the technological progress
for these nanometer-sized specs of semiconductor matter, and weighs
the remaining challenges on the path to widespread commercialization
for this promising technology with applications in everything from
TVs to highly efficient sunlight collectors.



FULL STORY ==========================================================================
A new article in Science magazine gives an overview of almost
three decades of research into colloidal quantum dots, assesses the technological progress for these nanometer-sized specs of semiconductor
matter, and weighs the remaining challenges on the path to widespread commercialization for this promising technology with applications in
everything from TVs to highly efficient sunlight collectors.


========================================================================== "Thirty years ago, these structures were just a subject of scientific
curiosity studied by a small group of enthusiasts. Over the years,
quantum dots have become industrial-grade materials exploited in a range
of traditional and emerging technologies, some of which have already found their way into commercial markets," said Victor I. Klimov, a coauthor
of the paper and leader of the team conducting quantum dot research at
Los Alamos National Laboratory.

Many advances described in the Sciencearticle originated at Los Alamos, including the first demonstration of colloidal quantum dot lasing, the discovery of carrier multiplication, pioneering research into quantum
dot light emitting diodes (LEDs) and luminescent solar concentrators,
and recent studies of single-dot quantum emitters.

Using modern colloidal chemistry, the dimensions and internal structure
of quantum dots can be manipulated with near-atomic precision, which
allows for highly accurate control of their physical properties and
thereby behaviors in practical devices.

A number of ongoing efforts on practical applications of colloidal
quantum dots have exploited size-controlled tunability of their
emission color and high- emission quantum yields near the ideal 100
percent limit. These properties are attractive for screen displays and lighting, the technologies where quantum dots are used as color converting phosphors. Due to their narrowband, spectrally tunable emission, quantum
dots allow for improved color purity and more complete coverage of the
entire color space compared to the existing phosphor materials. Some of
these devices, such as quantum dot TVs, have already reached technological maturity and are available in commercial markets.

The next frontier is creating technologically viable LEDs, powered by electrically driven quantum dots. The Science review describes various approaches to implement these devices and discusses the existing
challenges.

Quantum LEDs have already reached impressive brightness and almost
ideal efficiencies near the theoretically defined limits. Much of this
progress has been driven by continuing advances in understanding the performance-limiting factors such as nonradiative Auger recombination.



==========================================================================
The article also discusses the status and challenges of
solution-processable quantum dot lasers.

"Making these lasers available would benefit a range of technologies,
including integrated photonic circuits, optical communication,
lab-on-a-chip platforms, wearable devices, and medical diagnostics,"
Klimov said.

Los Alamos researchers have contributed key advances in this area
including the elucidation of mechanisms for light amplification in
colloidal nanostructures and the first demonstration of a lasing effect
using these materials.

"The primary current challenge is demonstrating lasing with electrical pumping," Klimov said. "Los Alamos has been responsible for several
important milestones on the path to this objective including the
realization of optical gain with electrical excitation and the development
of dual-function devices that operate as an optically pumped laser and
a standard electrically driven LED." Quantum dots are also of great
potential utility in solar harvesting and light sensing technologies. Due
to their tunable bandgap, they can be engineered to target a particular
range of wavelengths, which is especially attractive for realizing
inexpensive photodetectors for the infrared spectral range. In the
realm of solar energy technologies, colloidal quantum dots have been
exploited as active elements of both solar cells and luminescent sunlight collectors.

In the case of photovoltaics (PV), the quantum dot approach could be used
to realize a new generation of inexpensive, thin-film PV devices prepared
by scalable solution-based techniques such as roll-by-roll processing. In addition, they could enable conceptionally new photoconversion schemes
derived from physical processes unique to ultrasmall "quantum-confined" colloidal particles. One such process, carrier multiplication, generates multiple electron-hole pairs by a single absorbed photon. This process,
first reported by Los Alamos researchers in 2004, has been the subject
of intense research in the context of its applications in both PVs and
solar photochemistry.

"Another highly promising area is quantum dot luminescent solar
concentrators or LSCs," Klimov said. "Using the LSC approach, one can,
in principle, convert standard windows or wall sidings into power
generating devices. Along with roof-top solar modules, this could help
supply an entire building with clean energy. While the LSC concept
was introduced back in 1970s, it truly flourished only recently due
to introduction of specially engineered quantum dots." Los Alamos
researchers have contributed many important advances to the LSC field
including the development of practical approaches for tackling the
problem of light self-absorption and developing high-efficiency bi-layer (tandem) devices. Several start-ups, including a Laboratory spin-off,
UbiQD Inc., have been actively pursuing commercialization of a quantum
dot LSC technology.

========================================================================== Story Source: Materials provided by
DOE/Los_Alamos_National_Laboratory. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. F. Pelayo Garci'a de Arquer, Dmitri V. Talapin, Victor I. Klimov,
Yasuhiko Arakawa, Manfred Bayer, Edward H. Sargent. Semiconductor
quantum dots: Technological progress and future challenges. Science,
2021; 373 (6555): eaaz8541 DOI: 10.1126/science.aaz8541 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210805154733.htm

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