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LCD screens utilize a backlight of LEDs or a series of LEDs positioned at the edges of a screen to diffuse white light through polarizing filters, a liquid crystal layer, and a color filter. This arrangement leads to an image being displayed on the display surface. Fundamentally, the image on the screen is produced by blocking and filtering certain wavelengths of light from reaching the display surface. However, significant amounts of energy are wasted through this method.
Quantum dots are photo-emissive nanocrystals. They are capable of emitting monochromatic light naturally when they are excited by an energy source. When used in quantum dot-enhanced LCDs, a layer of quantum dots is positioned on top of a blue LED backlight, which emits all the blue light visible onscreen and supplies the energy needed for red and green quantum dots to emit their colors. Accurately tuning these colors can be achieved by controlling the size, shape, and chemical composition of the nanocrystals. This changes their emitted wavelengths precisely and produces a more vibrant display and a wider color gamut, which is a requirement for modern Ultra-HD and HDR displays.
How are Quantum Dots Made?
What constitutes a nanoparticle is determined by the particle’s size and geometry. Nanoparticles must be below 100 nanometers (nm) to qualify as a nanoparticle, a miniscule scale that is essential for defining a material’s mechanical properties.
Transparent or crystalline particles of nanomolecular dimensions can emit monochromatic light in wavelengths particular to their dimensions. For example, quantum dots weaken light photons when excited by a light source. This results in conduction bands inside the nanoparticle. When excited electrons return to the outer orbit of the atom from these conduction bands, they emit light. The wavelength of this light is determined by the atomic distance between the conductive band and the outer orbit of the nanoparticle.
This fluorescent behavior is facilitated by certain properties in nanoparticles, which allow them to display similar mechanical properties to those seen in atoms. Quantum dots in a range of sizes are generally included in samples or dispersions, allowing products to use or display the whole of the wavelength spectrum.
Can Quantum Dot Displays Compete with OLED Displays?
OLED displays are the main source of competition for LCD technology, as they offer technically infinite contrast ratios along with thinner, more lightweight displays. OLED technology is made up of an organic, carbon-based film placed between two conductors that emit light when a current is passed through it.
The ability to emit light itself means that this type of diode does not need an LED backlight to function. OLED technology also allows for the display of true black colors on the display surface, because every individual pixel can be switched on and off without light from the LED backlight bleeding in front the neighboring pixels. This technology also produces the highest efficiency levels.
However, the OLED display market has been negatively affected by low manufacturing yields and expensive material costs. This is particularly true in the manufacturing of the large panels used in modern TVs. The production of OLED technology is becoming more stable, but the costs of marketing the technology and related products remain high.
Similarly, quantum dot production is costly. However, recent developments in the chemistry involved in the technology may lead to a large-scale manufacturing breakthrough emerging quantum dot tech.
Present generations of LCDs enhanced by quantum dots use them based on chemical compositions made up of cadmium selenide or indium phosphide. Both cadmium selenide and indium phosphide have limited availability and are immensely expensive, with costs in the region of $10,000 per kilogram. These two chemicals also need an additional, inorganic shell to achieve sufficient levels of quantum efficiency.
To resolve this problem, Avantama has developed quantum dots comprising cost-effective cesium lead halide, which do not require an inorganic shell and their absorbance per gram is at least three times higher than quantum dots comprising different chemical compositions. At present, these metal halide perovskite quantum dots yield the highest possible quantum efficiencies, and as a result produce the best peak brightness in LCDs.
Next-Generation Quantum Dot Displays
This technology will be very influential for the next generation of LCD screens, in which color filters are replaced with thermally efficient quantum dots. As previously explained, color filters omit wavelengths of light to show colors on screen. As a result, a high amount of the light emitted by the display’s LEDs is wasted.
To improve this level of waste and enhance the energy efficiency, naturally produced monochromatic light from a layer of quantum dot-pixels behind a liquid crystal display layer would be an advantageous tool. This technique would also offer top-of-the-range optical performance. Avantama’s quantum dot products are already suitable to manufacture these types of color filter displays.
Existing quantum dot displays make use of the photo-luminescent nature of these nanocrystals to offer extremely pure light by exciting them with an LED-based light source. Future iterations could transform that technology by utilizing the electro-luminescent elements of quantum dots in the production of direct-view quantum dot displays, and omitting the liquid crystal display entirely.
By doing this, unparalleled picture quality with a wider color gamut, exceptional contrast levels, improved viewing angles, and unrivaled levels of efficiency could be achieved. This range of benefits, while sharing likenesses to OLED technology, would dramatically change the dynamic in display technology, making it hard for OLED to dominate the display market.
Quantum Dots from Avantama
Avantama is a leading developer and supplier of cutting-edge nanoparticles and solutions for a range of industrial sectors. We are dedicated to providing the most mechanically stable quantum dots and improving the production processes of emerging materials to ensure industry standards are consistently safe and sustainable.
If you need more information about our cadmium-free quantum dots, contact us today.
This information has been sourced, reviewed and adapted from materials provided by Avantama AG.
For more information on this source, please visit Avantama AG.