Quantum dots are tiny nanoparticles with very interesting optoelectronic properties and a range of real-life applications in electronics such as displays, solar cells, and sensors. Because of their properties and small size, they are sometimes called artificial atoms or zero-dimensional nanomaterials.
Content
- What is a Quantum dot?
- How do you make them
- Applications
- Challenges to Quantum dots
- Outlook on Market
What is a Quantum dot?[i],[ii]
Quantum dots are made from metals or semiconductor materials, usually with two-three different elements in a crystal structure. They are typically the size of 1-10 nanometers and normally need to be coated by another material that ensures they don’t degrade, in other words making them stable at a specific size. An example is gold nanoparticles that are coated by a layer of a carboxylic acid. Another popular material choice is CdSe (Cadmium selenide), but quantum dots can be made from many other materials including heavy metal free such as silicon and carbon.
At very small sizes, particles behave similarly to atoms in the way that their energy bands are discrete, meaning the color of the light they emit or absorb is at a very precise wavelength. This property is what makes them excellent for applications such as displays.
How do you make them?
There are different chemical methods. The challenge is to find a method that gives a good yield while controlling the size of the particles. The method used mostly depends on the application. If the quantum dots need to be in a liquid, the best way would be a chemical bottom-up method where you create a large batch and add chemicals with a high temperature for specific amounts of time. This method is known as colloidal synthesis. [i]
If the quantum dots are instead needed as a powder, a method known as plasma synthesis can be used to produce them in the gas phase. [iii]
In addition, other methods to produce quantum dots include top-down fabrication using etching.
Applications
An application where quantum dots have highly succeeded is within displays. Companies such as Sony, Samsung, and LG have all made great products with quantum dots integrated into the display, branded as QLED displays. By doing that, they can produce a wider range of colors, giving a much more vivid experience.
Quantum dots for displays are produced by companies such as Nanosys Inc. with a range of options, some which are heavy-metal free.
Solar cells are a very promising market for quantum dots as they can be engineered to absorb a larger amount of light from the sun, with other materials having a narrower spectrum of possible wavelengths they can absorb[v]. Currently, silicon is widely used as it is the main component in modern-day electronics. This is the case even though there are fundamental limits to its efficiency with many other materials such as quantum dots providing a much higher theoretical efficiency. Now, however, there are no commercial quantum dot solar cells available, and the area needs more research and funding.
Other interesting applications are within LEDs, lasers[vi], and for sensors used for medical imaging[vii].
Challenges to quantum dots
One of the main challenges to the application of quantum dots is that they are often toxic and can interact with living cells. Hence, even though they possess excellent abilities relevant for medical applications, they are not likely to be applied in that field soon as regulations are high and very precautious. The toxicity is primarily due to heavy metals such as Cadmium often being part of the building materials.
Another challenge that is common for new materials is when they have to compete in industries that have specialized in working with other materials such as silicon. This is especially the case with solar cells as it is very hard to suddenly make the switch when production has already been optimized for something else. Thus, it requires more than scientific breakthroughs but a lot of investment and some patience.
As for other novel technologies, newly developed quantum dots often face the challenge of scalability. The synthesis at larger amounts takes some research to get right so it is an important aspect to keep in mind when looking at quantum dots from new materials.
Outlook on Market
Quantum dots seem to have come to stay within electronic displays, as big companies such as Samsung are investing highly in this technology[viii]. Furthermore, there is a well-established supply chain with companies such as Nanosys Inc. providing reliable and high-quality material.
The expectations for quantum dots are high, MarketsandMarkets predicts an increase in market size from USD 3.5 billion in 2020 to USD 10.6 billion by 2025[ix] (annual growth: 24.6 %) with the growth mainly from applications in displays. Meanwhile, the incentives to apply it in other markets such as solar cells are growing with large amounts of research being done[x].
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References
[i] Chemistry at the Nanoscale, DTU Chemistry, 2020, p. 16-23
[ii] What is a Quantum Dot, accessed at: https://www.nanosysinc.com/quantum-dot-basics
[iii] https://www.researchgate.net/publication/301290274_Plasma_Synthesis_of_Nanoparticles
[v] https://www.intechopen.com/books/solar-cells-new-approaches-and-reviews/quantum-dots-solar-cells
[vi] https://www.laserfocusworld.com/lasers-sources/article/14074945/colloidal-quantumdot-laser-diodes-could-be-coming-soon
[vii] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5546783/
[viii] https://nanophotonica.com/nanophotonica-announces-3-5m-investment-led-by-samsung-ventures/
[ix] https://www.marketsandmarkets.com/Market-Reports/quantum-dots-qd-market-694.html?gclid=EAIaIQobChMIvZ2-qdf36wIVSubtCh1JDAj5EAAYASAAEgLfv_D_BwE
[x] https://scitechdaily.com/solar-technology-breakthrough-world-record-quantum-dot-solar-cell-efficiency/