Quantum dots, tiny particles of matter that emit light at specific wavelengths can be tuned. This is just one of the many qualities that make them useful in a variety of technology applications. Credit: Los Alamos National LaboratoryScience magazine has published a new article that provides an overview of nearly three decades of research on colloidal quantum dots. It also assesses technological progress for these tiny specs of semiconductor matter and weighs the remaining obstacles to commercialization of this promising technology, which could be used in everything, from televisions to highly efficient solar collectors.These structures were a matter of scientific curiosity, only a few people had ever seen them. "Quantum dots have evolved into industrial-grade materials over the years," stated Victor I. Klimov (coauthor of the paper) and head of the quantum dot research team at Los Alamos National Laborator.Los Alamos was the origin of many of the Science articles, including the first demonstrations of colloidal quantum dots lasing, discovery of carrier multiplication and pioneering research into quantum dot lights emitting diodes (LEDs), luminescent solar concentrators and the recent study of single-dot quant emitters.Modern colloidal chemistry allows you to manipulate the dimensions and inner structure of quantum dots with almost atomic precision. This allows you to control their physical properties and behavior in practical devices.Many ongoing research efforts into practical applications of colloidal quantum dots have focused on the size-controlled tuning of their emission colors and high-emission quantum yields close to the ideal 100 percent limit. These properties are appealing for screen displays and lighting. This is where quantum dots are used to convert phosphors into color. Quantum dots have a narrowband, spectrally-tunable emission that allows for better color purity and a wider coverage of the whole color space than existing phosphor materials. These devices, including quantum dot TVs have reached technological maturity and are now available on the commercial market.Next is the creation of technologically feasible LEDs powered by electrically-driven quantum dots. This Science review discusses various implementation options and the challenges. Quantum LEDs are already achieving impressive brightness and efficiencies that are close to the theoretical limits. This is largely due to continued advances in understanding performance-limiting factors like nonradiative Auger Recombination.This article also addresses the challenges and status of solution-processable quantum dots lasers.Klimov stated that making these lasers accessible would benefit a variety of technologies including integrated photonic circuits and optical communication platforms, lab-on a chip platforms, wearable devices and medical diagnostics.Los Alamos researchers made important contributions to this field, including the discovery of light amplifier mechanisms in colloidal nanostructures and first demonstration of a lasing effect with these materials.Klimov stated that the primary challenge in lasing with electric pumping is to demonstrate it. "Los Alamos was responsible for many important milestones along the path to this goal, including realization of optical gain using electrical excitation and development of dual-function devices which operate as both an optically pumped and standard electrically driven laser.Quantum dots can also be used in light sensing and solar harvesting. Because of their narrow bandgap, it is possible to target specific wavelengths. This makes them attractive for creating inexpensive photodetectors in the infrared spectrum. Colloidal quantum dots are used in solar energy technologies as active elements.The quantum dot approach to photovoltaics could be used to create a new generation thin-film PV devices that are affordable and made using scalable solution-based methods such as roll-by–roll processing. They could also be used to create new photoconversion schemes that are based on physical processes only possible with ultra-small colloidal particles. Carrier multiplication is a process that generates multiple electron-hole pairs from a single photon. Los Alamos researchers first reported this process in 2004. It has been the focus of intensive research for its applications in PVs and solar photochemistry.Klimov stated that quantum dot luminescent sun concentrators, or LSCs, are another promising area. The LSC approach can be used to convert standard windows and wall sidings into power-generating devices. This could be used to provide clean energy for entire buildings, along with rooftop-top solar panels. Although the LSC concept was first introduced in 1970, it has only been able to thrive since then due to the introduction of quantum dots.Los Alamos researchers made many significant contributions to the LSC field, including practical approaches for solving the problem of light selfabsorption and the development of high-efficiency bilayer (tandem), devices. UbiQD Inc., a Laboratory spinoff, has been actively involved in commercialization of the quantum dot LSC technology.You are close to the Colloidal quantum dots laser diodes.More information: F. Pelayo Garca de Arquer et al, Semiconductor quantum dots: Technological progress and future challenges, Science (2021). Journal information: Science F. Pelayo Garca de Arquer et al, Semiconductor quantum dots: Technological progress and future challenges,(2021). DOI: 10.1126/science.aaz8541
