Quantum dot display or QD display is a specific display technology that uses semiconductor nanocrystals called quantum dots to produce pure monochromatic red, green, and blue lights.
Take note that a nanocrystal is any material or more specifically, a crystalline particle with at least one dimension measuring less than 100 nanometers. On the other hand, a quantum dot is a type of nanocrystal with semiconducting properties. They measure between two to ten nanometers.
When used as a display technology, quantum dots have optical properties that make them more efficient than larger light-emitting diodes and liquid crystals. These dots are either photoluminescent or electroluminescent.
Photoluminescent quantum dots are photo-emissive, and they glow a particular color after being illuminated by light. On the other hand, electroluminescent quantum dots are electro-emissive, and they produce light and color in response to the passage of an electric current or strong electric field. Either of the two, the colors produce depend on the size of the quantum dot: larger ones emit reds while smaller ones emit blues.
Nonetheless, the advantageous properties of of nanocrystals and quantum dots provide the core advantages of QD displays.
The Pros of QD Displays: What are the Advantages or Benefits of Quantum Dot Display?
The primary advantage of using quantum dots in display technology centers on their ability to produce pure monochromatic red, green, and blue light. Note that conventional LED-based LCDs do not efficiently produce saturated colors because they primarily depend on white LEDs for backlighting that produce broad light spectrum.
On the other hand, QD-based displays directly use the light from either the blue LEDs to produce color from each photoluminescent quantum dot or the application of electric current to produce color from each electroluminescent quantum dot. Hence, quantum dot displays naturally produce monochromatic lights that collectively result in the production of highly saturated narrow band primary colors.
The following are the specific advantages of quantum dot display:
Ultra HD Applications
A specific benefit of QD displays is improved color accuracy than conventional LCDs. Remember that quantum dots produce light depending on their size. These dots can be tuned precisely to produce a specific color of light that in turn, correspond to a particular color.
LCDs based on QD technology can also compete with OLED displays in terms of color saturation. Note that conventional LCDs have smaller color gamut than OLED. However, through quantum dot technology, an LCD can have 40 to 50 percent higher color gamut than conventional LCDs, thus competing head-to-head with OLED displays.
Furthermore, when compared to conventional LCDs, some QD displays, particularly those based on photoluminescence such as the QLED display from Samsung, produce light and color directly. Note that conventional LCDs need backlighting from LEDs to make colors visible.
Backlighting distorts the pureness of the color and reduces the contrast ratio of a particular display due to the impossibility of deep blacks. Photoluminescent QD displays can produce deep blacks because they natively control the light emitted via individual quantum dots. The result is a contrast ratio that closely matches OLED displays.
On the other hand, those QD displays based on electroluminescence have brighter output than OLED displays because of the additional backlighting to make the colors more visible. Hence, these QD displays are considerably brighter than OLED displays, especially when viewed under direct light or outdoors under sunlight.
The advantages such as better color accuracy, higher color saturation, possibly wider contrast ratio, and higher peak brightness have made quantum dot technology ideal for producing displays capable of ultra-high definition. The Ultra HD Alliance has a standard for Ultra HD Premium TVs that require the application of quantum dot technology for LED-based LCDs.
Longer Lifespan and Energy Efficiency
Color degradation is a key disadvantage of OLED displays due to the natural and faster degradation of organic materials and vulnerability to water damage. Color-specific organic materials in an OLED panel have varying degradation rate. Red and green materials have a longer lifespan than blue materials. What this means is that OLED displays will develop noticeable screen burn-ins overtime as blue materials degrade faster than red and green ones.
On the other hand, when applied to LCDs, quantum dot technology has the advantage of having a longer lifespan than OLED displays. Take note that LCD technologies such as twisted nematic and in-plane switching technologies are naturally more durable than OLED displays because they do not suffer from uneven color and material degradation, as well as susceptibility to water damage.
Quantum dot technology can also save 20 percent of power than conventional LCDs according to paper. This is especially true for QD displays based on electroluminescent quantum dots. Similar to OLED displays, note that to make colors visible, these electron-emissive QD displays are similar to OLED displays because they do not rely solely on backlighting. Remember that electroluminescent quantum dots produce not only color but also light directly without the need for accompanying backlighting via LED.
Another reason behind the energy efficiency of QD displays, whether they are based on photoluminescent or electroluminescent quantum dots, is the fact that using nanocrystals or more specifically, quantum dots render as much as a 30 percent increase in the visible light spectrum, thus making them brighter than larger crystalline used in conventional LCDs while using 30 to 50 percent less power.
Precise display of colors also gives QD displays energy efficiency. Conventional LCDs can waste energy combining and balancing different colors. However, remember that a quantum dot display produces only the necessary color of a given image for a given time.
Wider and Promising Applications
Take note that a quantum dot display can either be based on LCD technology or OLED display technology. Essentially, quantum dot technology can be applied in LCDs, such as in the case of QLED from Samsung, as well as in LED and OLED displays, such as in the case of so-called true QD-LED hybrid.
Because of the possible integration of quantum dot technology with other display technologies, the applications include new-generation televisions, computer monitors and laptop displays, smartphones and other mobile devices, and other consumer electronic devices. These applications can make Ultra HD a standard in the mass market.
It is also interesting to note that manufacturing quantum dot displays has become efficient, thus translating to reasonable production costs. In fact, the cost of making QD-based LCDs is cheaper than manufacturing OLED displays. Considering the advantages of quantum dot technology, these QD-based LCDs can easily compete against OLED displays in the market.
The application of quantum dot technology can also result in the production of large and flexible LCDs, thus competing once again with plastic OLEDs, including flexible OLEDs. Because OLED displays have a higher degradation rate and therefore, shorter lifespan, QD-based LCDs have more practical applications.
The Cons of QD Displays: Disadvantages of Quantum Dot Display
It is important to reiterate the fact that quantum dots are either photoluminescent or electroluminescent or in other words, either photo-emissive or electro-emissive. Current QD displays in the market, such as the QLED TVs from Samsung, are based on photoluminescence in which the quantum dots produce light and color through exposure to a light source.
Quantum dot displays based on electroluminescence are still experimental although it is possible for them to be available in the mass market soon. Note that these displays have quantum dots that produce light and color in response to the passage of an electric current or strong electric field. The resulting product has been dubbed as a true QD-LED or Quantum LED display because it uses light-emitting quantum dots.
Nonetheless, the introduction of photo-emissive and electro-emissive QD displays in the market could create confusion on the part of the consumers. Some advantages of quantum dot displays such as contrast ratios and better energy efficiency are unique to the photoluminescence variant. In the same manner, some advantages of QD displays such as higher brightness peak are exclusive to the electroluminescent variant.
Quantum dot technology is also applicable in other display technologies. Researchers and companies such as Samsung have been working on incorporating this technology with OLED technology. Hence, a QD display is essentially an ambiguous term for a particular type of display technology.
Remember that quantum dot technology can be incorporated into other display technologies. What this means is that the advantages and disadvantages of a particular QD display will be influenced significantly by its accompanying display technology.
In a nutshell, the following are the disadvantages and limitations of quantum dot displays:
• A QD display based on LCD will have slower response time than OLED displays in general. Take note that in-plane switching LCD technology is known for slower response rates that make them unsuitable for video gaming and other applications that require high frame rates.
• Poorer viewing angle, when compared to OLED displays, is another disadvantage of a QD LCD. In most IPS LCDs, image quality as determined by color and contrast diminishes when a viewer moves away from the center of the screen.
• Essentially, a QD LCD inherits all of the drawbacks of the general LCD technology, including the cons of IPS LCD such as limited contrast ratio, considerable power inefficiency, and slow pixel response time when compared to OLEDs.
• Better lifespan is one of the notable advantages of QD displays based on LCD when compared to an OLED display. However, applying quantum dot technology with OLED technology would mean that the resulting display would have a shorter lifespan due to susceptibilities in screen burn-ins and water damage.
• A QD OLED display inherits all of the drawbacks of OLED display technology such as poor outdoor visibility, uneven degradation of pixels, immediate and irreparable damage due to water exposure, and predisposition to oversaturation and color inaccuracy.
