Buzz
Recently, there's news that Samsung won't pursue OLED anymore but is transitioning to a new technology called QLED. The 'Q' here stands for Quantum, as this technology utilizes quantum dots to emit light pixels.
1. What's the new trademarked 'QLED' screen that Samsung just registered, and how does it differ from current quantum TVs?
Recently, there's information that Samsung is shifting away from OLED to embrace QLED, a new technology utilizing quantum dots for luminance. What sets it apart from current quantum displays?
Summarizing the main points:
- Quantum dots (QD) are nano-sized material particles.
- Quantum dots are currently used in some TVs and laptop/tablet screens within the backlight layer. The fundamental display remains LCD, with quantum dots acting as a film or tube to enhance image quality. Reds appear truer, as do blues and greens.
- Future QLED TVs will embed quantum dots directly into pixels. Sony has attempted this but hasn't succeeded yet.
- OLED and QLED both feature self-emissive pixels, eliminating the need for a backlight like LCDs. The key difference is OLED employs organic materials for emission, while QLED uses inorganic materials. Sony's inorganic LED technology CLEDIS has reached micrometer-scale, but not nanometer-scale yet.
- No commercialized QLED products have launched due to manufacturing complexities and economic considerations.
- There are no comparative studies yet on image quality between QLED and OLED.
What exactly are quantum dots?
Quantum dots aren't a recent invention. They were discovered over 30 years ago by Russian scientists Alexander Efros and Aleksey Ekimov, alongside Louis Brus. These scientists noticed that a reaction in a solvent would produce particles of various sizes, and depending on the size, they could achieve any color within the light spectrum.
The scientific definition of quantum dots goes like this: Quantum dots (QD) are tiny material particles (around a few nanometers, about 10nm) wherein adding or removing an electron alters their properties in a useful manner. Due to spatial constraints (or confinement) of electrons and holes in the material (a hole forms due to the absence of an electron; a hole acts as a positive charge), quantum effects emerge, altering the material's properties. When we excite a QD, the smaller it is, the higher its energy and brightness. Hence, QDs open the door to a range of new technological applications.
By refining physical formulas, one can produce particles (also called dots) capable of emitting blue, green, red, and many other colors when subjected to electricity. The size of the dot also influences its color. Previously, the color range of quantum dots has proven highly effective in the solar panel industry as they enhance light absorption. In the field of optoelectronics, when mixed together, quantum dots improve electron microscope lenses.
Quantum dots in today's TVs: situated in the backlight, yet fundamentally LCD TVs
Before delving into QLED, let's take a look at how quantum dots are currently utilized in TVs. In 2013, Sony introduced a technology called Triluminos for around ten-inch LCD screens, primarily for laptops. Sony touted it as the first consumer product featuring quantum dots. Subsequently, the company incorporated Triluminos into its high-end TV models in 2014. By late 2014 and early 2015, other companies followed suit, including Samsung, LG, TCL, and several other renowned brands. Amazon Kindle Fire HDX, Asus Zenbook NX500, VAIO Fit 13A are among the products employing quantum dots.
One thing to note is that the quantum dots used in these TVs are all situated in the BACKLIGHT LAYER, not within the LCD panel used to display content. Current LED-backlit LCD screens utilize high-intensity blue LEDs coated with a phosphor layer to create white light. This light then passes through a filter with three primary colors: red, blue, and green, forming the image you see on the screen. However, this component has low selectivity, for instance, the red filter still allows some orange light to pass through. When red and green aren't pure, they produce an image that appears somewhat dull. Yet, due to design efficiency, power, and production costs, LED-backlit LCD TVs are still being used today. Some brands add local dimming technology to dim certain areas, but only for high-end TV models.
In contrast, 'quantum dot' TVs will use LEDs WITHOUT A COATING placed in a glass tube filled with red and green quantum dots. These two types of dots will absorb some blue light from the backlight and emit pure red and green light. With this method, light passing through the red filter will carry the correct red color, similarly for the other colors. As a result, we achieve more accurate color reproduction and better image quality compared to using phosphor-coated LEDs. Additionally, another implementation of quantum dot displays applied by 3M is to place a film with quantum dots on top of the backlight. The operating principle of this solution is similar to directly placing quantum dots into the backlight.
Quantum dots in future QLED TVs: Embedded within the pixels
Returning to Sony, the first company to incorporate quantum dots into consumer devices. Sony's initial intention was to use quantum dots to create pixels on the screen, which would emit light through transistors when powered. Although QD Vision, the company supplying quantum dots to Sony, developed a prototype of this type of display, it's extremely challenging to produce on a large scale. Hence, both companies shifted to using quantum dots in the backlight. QD Vision promises that its product can provide color similar to high-quality CRT screens and come close to OLED screens' quality.
This forms the foundation for QLED technology: utilizing quantum pixel displays. And since these pixels are capable of self-emission, there's no need for a backlight like LCDs. Currently, OLEDs also don't require a backlight, allowing both QLED and OLED to achieve deep blacks with excellent contrast as the black areas of the image will completely turn off. Coupled with the benefits of color accuracy as mentioned above, you might have guessed why there are rumors that Samsung wants to ditch OLED in favor of QLED.
Note: In this article, I use the term 'QLED' for brevity, but if the rumors are true, this brand belongs to Samsung. In that case, other brands will have a different term to refer to their quantum dot displays.
The difference between QLED and OLED in terms of structure lies in the type of chemicals used to create pixels. OLED uses organic compounds to create light-emitting materials, hence the 'O' - organic. An example of an organic compound used in OLED production is Tris (8-hydroxyquinolinato) aluminum (C27H18AlN3O3). Meanwhile, QLED utilizes inorganic compounds, such as InP/ZnS or CuInS/ZnS. In the past, CdSe was used to create quantum dots, but due to its containing the toxic element Cadmium, it wasn't suitable for commercial products.
Earlier this year, Sony introduced a technology called CLEDIS. It's the next step of the Crystal LED technology that the company introduced in 2012 with a TV prototype. CLEDIS also employs self-emitting pixels and doesn't require a backlight. Sony hasn't publicly disclosed whether the materials inside these LEDs are organic or inorganic, but since Sony previously mentioned they deliberated between Crystal LED and OLED, we can tentatively assume CLEDIS uses inorganic material. CLEDIS targets screens used in professional settings, such as studios, factories, and museums, rather than consumer products, perhaps due to the high cost. Nonetheless, CLEDIS still boasts superiority over LCD with significantly brighter, higher-contrast, and better color reproduction.
However, CLEDIS is not QLED, as it doesn't use quantum dots and still relies on LED cells with micrometer sizes, while quantum dots, by definition, must be down to nanometers. Sony also doesn't mention the word 'quantum' on websites discussing CLEDIS.
The quantum dot vials made of CdSe are produced by the Nanoco company
Currently, there are still no genuine QLED screens introduced or sold. No company has officially mentioned the production process of QLED TVs, and if mentioned, it's primarily in the product development stage. Since quantum dots need to be manufactured at the nano-material level, it's clear this isn't a simple matter. Matters become even more complex when you have to produce in large quantities and at low costs, or else nobody will buy your product. It's a problem that companies like Samsung, Sony, and LG have to solve. Rumors about Samsung dealing with QLED also suggest that it won't be until 2018 or 2019 that these types of TVs start to appear.
Reading this, you might ask whether quantum dot displays offer better color than LCD, brighter than LCD TVs, better contrast than LCD, what about compared to OLED? Unfortunately, I couldn't find any documents comparing OLED TVs with QLED, nor have I witnessed and compared them firsthand, so my answer is I don't know. I only found information that quantum dot luminescent materials are better than organic luminescent materials in the following aspects:
- Higher brightness, up to 20 times brighter
- More accurate color reproduction
- Better photon leakage control, meaning preserved colors
- Higher durability, longer lifespan
Similar scenarios have unfolded with OLED as well, where the high commercial production costs have driven up TV prices, leading many manufacturers to shift away from large-sized OLEDs despite their benefits. It's evident that devising excellent technology is one thing, but successfully bringing it to market is an entirely different challenge. I remain hopeful that QLED will succeed because then we'll have TVs that are fancier, more beautiful, and more pleasing to the eye. Let's wait and see!
