How Does a Quantum Dot LCD Actually Work?

The display market is awash in technological acronyms designed to compress key performance indicators and complex terminologies into an easily marketable format. Ultra-high definition becomes UHD while organic light-emitting diodes are expressed as OLEDs. This is not a new aspect of the industry, but it is an increasingly important one as manufacturers look to implement cutting-edge technologies like quantum dots in different ways.

Quantum dots are among the most versatile components in next-generation display manufacturing. As a result, they have been implemented in a host of different device architectures that are prescribed distinct terminologies:

  • Quantum dot color filters (QDCF); not currently available at commercial markets, although they are widely envisaged as the next major breakthrough in quantum dot display technologies.
  • Quantum dot light emitting diodes (QD-LED/QLED); refer to various proprietary and prototypical display technologies that seek to combine the benefits of OLEDs with the outstanding emission properties of quantum dots.
  • Quantum dot liquid crystal displays (QD-LCD); are the most firmly-entrenched quantum dot-enhanced display technologies currently available at commercial scales.

This blog post will explore the working principles of quantum dot LCDs in more depth.

How Do Conventional LCDs Work?

Quantum dot enhanced LCDs exploit the same basic principles of conventional LCD technology. It is not a reinvention, but a significant leap forward in terms of performance, efficiency, and architectural variation.

A basic LCD is comprised of at least three components: a backlight of LEDs that emit monochromatic white light; a series of red, green, and blue (RGB) color filters; and a liquid-crystal layer that formats these colors into an image by controlling the emission of distinct pixels across the full display. The backlight provides illumination which is separated into RGB peak wavelengths by the color filters. The liquid crystal layer modulates the emission of these colors at distinct subpixels, individually controlling light emission across the full screen on a pixel-to-pixel basis. This is how an image is reproduced on screen, yet it has its limitations.

Typically, LCD backlights are comprised of blue LEDs coated in a broad spectrum yellow phosphor which produces a quasi-white light. These are used as conventional LEDs struggle to generate true, monochromatic white light which causes colorimetric restrictions: low intensity in peak wavelengths, a reliance on color balancing software, generally poor efficiency, etc. Quantum dots have been introduced to resolve this inherent drawback of LCD technology.

How Quantum Dot LCDs are Made

Quantum dots are semiconducting nanocrystals that emit light of finely-tuned wavelengths when excited by light or electricity. These are defined by the individual crystal’s size and chemistry which enables formulators to generate nanocrystals with tailored optical properties and outstanding quantum efficiencies. When integrated into an LCD matrix, quantum dots can eliminate issues associated with phosphor-coated blue LEDs.

In a prototypical quantum dot LCD, the backlight unit is comprised of blue LEDs without a phosphor coating. A film of red and green quantum dots is overlaid on the backlight, combining to produce a high-purity source of white light. This helps to produce brighter, more accurate images on-screen, resulting in the best performing LCD TVs currently available. The typical quantum dot LCD arrangement can support a range of additional KPIs and techno-acronyms including HDR, UHD, 4K, and WCG.

Read More: OLED Vs. LCD: What's the Difference?

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