What Are Quantum Dots, And What Are They Actually Used For?

Quantum dots are nanoscale semiconductor crystals that make up core materials used in display screens, bio-marking, photovoltaics, short-wave infrared sensing, quantum computing, and more. The science behind it is actually quite simple: quantum dots have discrete rather than continuous energy levels due to their confined size. This matters because it's easier to control the energy the electron emits during the relaxation state in quantum dots. Also, this phenomenon is how you can fine-tune the exact color seen on your QLED screen.

The easiest way to understand how it works is to focus on the size of the quantum dots and how it relates to their electrical and optical characteristics. Small dots, around 2 nm in diameter, emit high-energy photons, producing blue and violet light. Medium dots, around 4 nm, emit mid-energy photons, producing yellow and green light, while large dots, around 6 nm, emit low-energy photons, producing red light. You can also numerically evaluate this by measuring the band gap; the change in energy between the excited and ground states is equal to Planck's constant multiplied by the speed of light, then divided by the wavelength.

In other words, the band gap is inversely proportional to the particle size. Because the emitted wavelengths and sizes can be easily controlled, quantum dots have attracted interest for various applications. They are used in screen technology, mainly in QLED and QD-OLED TVs and monitors. They are also used in biological imaging for receptor transport and intracellular signaling, and for their semiconductor properties in solar cells.

Besides making the colors more precise and pronounced in various QLED, mini-LED, and QD-OLED displays, quantum dots are also important for solar cells, which make up your solar panels, as well as in medical diagnostics and bio-imaging technology. With displays, quantum dots help your screens look brighter while giving you a broader color gamut; this is because quantum dots are more efficient with light emission, mainly because they produce no wasted wavelengths.

In layman's terms, it means there is less spread in the wavelength spectrum — when there is more, that can end up bleeding into other colors, thus requiring a filter. If you compare this to a traditional LCD screen, it often uses a white backlight that passes through green, red, and blue passive filters, which block unwanted wavelengths and produce the right colors. Quantum dots don't need to do that because most of their light energy is never lost to passive filtering.

While QLED displays benefit from this effect, they still rely on a transmissive LCD panel, which introduces at least one notable disadvantage of this panel type: the viewing angle on a QLED TV is more restrictive compared to OLED display types, since, ideally, you want to view the image straight ahead at the center. However, newer architectures like QD-OLED eliminate the LCD layer entirely, since they use quantum dots on top of self-emissive blue OLED pixels to achieve better contrast and wider viewing angles.