Quantum dots are tiny crystals that emit light with precisely controlled color values. Quantum dot LED technology significantly improves image quality without affecting the final cost of the devices, in theory :).
Conventional LCD TVs can only cover 20-30% of the color range that the human eye can perceive. The image is not very realistic, but this technology is not aimed at mass production of large display diagonals. Those who follow the TV market remember that back in early 2013 Sony introduced the first TV based on quantum dots (Quantum dot LED, QLED). Major TV manufacturers will release quantum dot TV models this year; Samsung has already presented them in Russia under the name SUHD, but more on that at the end of the article. Let's find out how displays produced using QLED technology differ from the already familiar LCD TVs.
LCD TVs lack pure colors
After all, liquid crystal displays consist of 5 layers: the source is white light emitted by LEDs, which passes through several polarizing filters. Filters located at the front and rear, together with liquid crystals, control the passing light flux, reducing or increasing its brightness. This happens thanks to pixel transistors, which affect the amount of light passing through the filters (red, green, blue). The generated color of these three subpixels, on which filters are applied, gives a certain color value of the pixel. The color mixing happens quite smoothly, but it is simply impossible to get pure red, green or blue this way. The stumbling block is filters that transmit not just one wave of a certain length, but a whole series of waves of different lengths. For example, orange light also passes through a red filter.
An LED emits light when voltage is applied to it. Due to this, electrons (e) are transferred from the N-type material to the P-type material. N-type material contains atoms with an excess number of electrons. P-type material contains atoms that lack electrons. When excess electrons enter the latter, they release energy in the form of light. In a conventional semiconductor crystal, this is typically white light produced by many different wavelengths. The reason for this is that electrons can be in different energy levels. As a result, the resulting photons (P) have different energies, which results in different wavelengths of radiation.
Light stabilization with quantum dots
IN QLED TVs Quantum dots act as a light source - these are crystals only a few nanometers in size. In this case, there is no need for a layer with light filters, since when voltage is applied to them, the crystals always emit light with a clearly defined wavelength, and therefore color value. This effect is achieved by the tiny size of a quantum dot, in which an electron, like in an atom, is able to move only in a limited space. As in an atom, the electron of a quantum dot can only occupy strictly defined energy levels. Due to the fact that these energy levels also depend on the material, it becomes possible to specifically tune the optical properties of quantum dots. For example, to obtain red color, crystals from an alloy of cadmium, zinc and selenium (CdZnSe), the size of which is about 10–12 nm, are used. An alloy of cadmium and selenium is suitable for yellow, green and blue colors, the latter can also be obtained using nanocrystals of a zinc-sulfur compound of 2–3 nm in size.
Mass production of blue crystals is very complex and expensive, so the TV presented by Sony in 2013 is not a “thoroughbred” QLED TV based on quantum dots. At the back of their displays is a layer of blue LEDs, the light of which passes through a layer of red and green nanocrystals. As a result, they essentially replace the currently common light filters. Thanks to this, the color gamut increases by 50% compared to conventional LCD TVs, but does not reach the level of a “pure” QLED screen. The latter, in addition to a wider color gamut, have another advantage: they save energy, since there is no need for a layer with light filters. Thanks to this, the front part of the screen in QLED TVs also receives more light than in conventional TVs, which transmit only about 5% of the luminous flux.
QLED TV with Quantum Dot Display from Samsung
Samsung Electronics presented premium TVs in Russia made using quantum dot technology. New products with a resolution of 3840 × 2160 pixels were not cheap, and the flagship model was priced at 2 million rubles.
Innovations. Curved Samsung SUHD TVs based on quantum dots differ from common LCD models in higher color rendering, contrast and power consumption characteristics. The integrated SUHD Remastering Engine allows you to upscale low-resolution video content to 4K. In addition, the new TVs received the Peak Illuminator and Precision Black intelligent backlight functions, Nano Crystal Color technology (improves the saturation and naturalness of colors), UHD Dimming (provides optimal contrast) and Auto Depth Enhancer (automatically adjusts the contrast for certain areas of the picture). The software basis of the TVs is the Tizen operating system with the updated Samsung Smart TV platform.
Prices. The Samsung SUHD TV family is presented in three series (JS9500, JS9000 and JS8500), where the cost starts from 130 thousand rubles. This is how much the 48-inch model UE48JS8500TXRU will cost Russian buyers. The maximum price for a TV with quantum dots reaches 2 million rubles - for the UE88JS9500TXRU model with an 88-inch curved display.
New generation TVs using QLED technology are being prepared by South Korean Samsung Electronics and LG Electronics, Chinese TCL and Hisense, and Japanese Sony. The latter has already released LCD TVs made using quantum dot technology, which I mentioned in the description of Quantum dot LED technology.
Quantum dot display
Quantum dots irradiated with ultraviolet light. Different sizes of quantum dots emit different colors.
To create a prototype, a layer of quantum dot solution is applied to a silicon board and a solvent is sprayed. A rubber stamp with a comb surface is then carefully pressed into the layer of quantum dots, separated and stamped onto glass or flexible plastic. This is how stripes of quantum dots are applied to a substrate. In color displays, each pixel contains a red, green, or blue subpixel. These colors are combined in varying intensities to create millions of shades. The researchers were able to create repeatable patterns of red, green and blue stripes by repeatedly using stamping technology. The stripes are applied directly to the matrix of thin-film transistors. The transistors are made from amorphous hafnium indium zinc oxide, which can carry higher currents and is more stable than conventional amorphous silicon (a-Si) transistors. The resulting display has subpixels about 50 micrometers wide and 10 micrometers long, small enough to be used in phone screens.
According to Seth Coe-Sullivan, founder and CEO of QD Vision, many problems have been solved by Samsung researchers and engineers, but the best quantum dot devices are not as efficient as OLED displays. It is also necessary to increase the service life, as the brightness of QLED displays begins to decrease after 10,000 hours.
Story
The idea of using quantum dots as a light source was first developed in the 1990s. In the early 2000s, scientists began to realize the full potential of quantum dots as the next generation of displays.
Notes
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LED, LCD, OLED, 4K, UHD... it would seem that the last thing the television industry needs right now is another technical acronym. But progress cannot be stopped, meet a couple more letters - QD (or Quantum Dot). Let me immediately note that the term “quantum dots” in physics has a broader meaning than is required for televisions. But in light of the current fashion for everything nanophysical, marketers of large corporations happily began to apply this difficult scientific concept. So I decided to figure out what kind of quantum dots these are and why everyone would want to buy a QD TV.
First, some science in a simplified form. A “quantum dot” is a semiconductor whose electrical properties depend on its size and shape (wiki). It must be so small that quantum size effects are pronounced. And these effects are regulated by the size of this very point, i.e. the energy of an emitted, for example, photon - in fact, the color - depends on the “dimensions”, if this word is applicable to such small objects.
Quantum-Dot TV from LG, which will be shown for the first time at CES 2015 In even more consumer language, these are tiny particles that will begin to glow in a certain spectrum if illuminated. If they are applied and “rubbed” on a thin film, then illuminated, the film will begin to luminesce brightly. The essence of the technology is that the size of these dots is easy to control, which means achieving accurate color.
The color gamut of QD TVs, according to QD Vision, is 1.3 times higher than that of conventional TV, and fully covers NTSC In fact, it is not so important what name large corporations choose, the main thing is what it should give to the consumer. And here the promise is quite simple - improved color rendition. To better understand how “quantum dots” will provide this, you need to remember the design of the LCD display.
Light under the crystal
An LCD TV (LCD) consists of three main parts: a white backlight, color filters (separating the light into red, blue and green colors) and a liquid crystal matrix. The latter looks like a grid of tiny windows - pixels, which, in turn, consist of three subpixels (cells). Liquid crystals, like blinds, can block the light flow or, on the contrary, open completely; there are also intermediate states.
The company PlasmaChem GmbH produces “quantum dots” in kilograms and packages them in vials When white light emitted by LEDs (LED, today it is difficult to find a TV with fluorescent lamps, as it was just a few years ago), passes, for example, through a pixel whose green and red cells are closed, then we see blue color. The degree of “participation” of each RGB pixel changes, and thus a color image is obtained.
The size of quantum dots and the spectrum in which they emit light, according to Nanosys As you understand, to ensure the color quality of the image, at least two things are required: accurate filter colors and the correct white backlight, preferably with a wide spectrum. It’s with the latter that LEDs have a problem.
Firstly, they are not actually white, in addition, they have a very narrow color spectrum. That is, the width of the spectrum of white color is achieved by additional coatings - there are several technologies, most often the so-called phosphor diodes with the addition of yellow are used. But this “quasi-white” color still falls short of the ideal. If you pass it through a prism (like in a physics lesson at school), it will not decompose into all the colors of the rainbow of the same intensity, as happens with sunlight. Red, for example, will appear much dimmer than green and blue.
This is what the spectrum of traditional LED lighting looks like. As you can see, the blue tone is much more intense, and green and red are unevenly covered by liquid crystal filters (lines on the graph) Engineers, understandably, are trying to correct the situation and come up with workarounds. For example, you can lower the green and blue levels in the TV settings, but this will affect the overall brightness - the picture will become paler. So all manufacturers were looking for a source of white light, the decay of which would produce a uniform spectrum with colors of the same saturation. This is where quantum dots come to the rescue.
Quantum dots
Let me remind you that if we are talking about televisions, then “quantum dots” are microscopic crystals that luminesce when light hits them. They can “burn” in many different colors, it all depends on the size of the point. And given that scientists have now learned to control their sizes almost perfectly by changing the number of atoms they consist of, it is possible to obtain a glow of exactly the color that is needed. Quantum dots are also very stable - they do not change, which means that a dot designed to luminesce at a certain shade of red will remain that shade almost forever.
This is what the spectrum of LED backlight looks like using QD film (according to QD Vision) The engineers came up with the idea of using the technology in the following way: a “quantum dot” coating is applied to a thin film, created to glow with a certain shade of red and green. And the LED is regular blue. And then someone will immediately guess: “everything is clear - there is a source of blue, and the dots will give green and red, which means we will get the same RGB model!” But no, technology works differently.
We must remember that “quantum dots” are located on one large sheet and they are not divided into subpixels, but simply mixed together. When a blue diode shines on the film, the dots emit red and green, as mentioned above, and only when all three of these colors are mixed does the ideal white light source appear. And let me remind you that high-quality white light behind the matrix is actually equal to the natural color rendering for the viewer’s eyes on the other side. At a minimum, because you don’t have to make corrections for loss or distortion of the spectrum.
It's still an LCD TV
The wide color gamut will be especially useful for new 4K TVs and 4:4:4 color subsampling, which awaits us in future standards. That's all well and good, but remember that quantum dots don't solve other problems with LCD TVs. For example, it is almost impossible to get perfect black, because liquid crystals (the same “blinds” that I wrote about above) are not able to completely block light. They can only “cover themselves”, but not close completely.
Quantum dots are designed to improve color reproduction, and this will significantly improve the impression of the picture. But this is not OLED technology or plasma, where the pixels are able to completely stop the flow of light. However, plasma TVs have retired and OLED TVs are still too expensive for most consumers, so it's still good to know that manufacturers will soon offer us a new kind of LED TV that will show better.
How much does a “quantum TV” cost?
The first QD TVs from Sony, Samsung and LG are promised to be shown at CES 2015 in January. However, China's TLC Multimedia is ahead of the curve, they have already released a 4K QD TV and say it is about to hit stores in China.
55-inch QD TV from TCL, shown at IFA 2014 At the moment it is impossible to name the exact cost of TVs with the new technology; we are waiting for official statements. They wrote that QDs will cost three times less than OLEDs with similar functionality. In addition, the technology, as scientists say, is very inexpensive. Based on this, we can hope that Quantum Dot models will be widely available and simply replace conventional ones. However, I think that prices will still increase at first. As is usually the case with all new technologies.
Until recently, organic light-emitting diode (OLED) TV displays were considered the last word in display technology. However, progress does not stand still and a new product is being brought to the attention of buyers - liquid crystal displays based on quantum dots.
Translated from English it actually means quantum dots. They are tiny particles with a diameter of only a few nanometers. It is impossible to see them with the naked eye. But this is their main advantage. By adjusting the size and giving a certain shape to this semiconductor, it is possible to exercise precise control over the electrical conductivity, and therefore change the color of the light emanating from the quantum dot. Large dots will appear red, smaller ones will appear blue, and medium ones will appear green. Thanks to its stability, as well as precise control over particle sizes, it is possible to obtain exactly the color that is needed. In this case, the given shade will be almost eternal.
Advantages of nanocrystals over LED
The displays of modern LED-backlit LCD TVs have a major drawback: their images depend on LEDs, which emit non-pure white light, and with a narrow color spectrum. There are certain technologies that make it possible to bring white closer to the ideal, but the resulting colors still do not have the same intensity (green and blue will be brighter than red). To somehow smooth out this difference, they use special color settings on the TV, lowering the blue and green values, but as a result, the image becomes much paler than necessary.
The problem of finding a source of ideal white light, which would provide the entire light spectrum with colors of the same intensity when refracted, was solved by using quantum dots.
Thus, when creating displays using nanocrystals, the following technology was used. Quantum particles of red and green shades are applied to a special film. They are not divided into subpixels as in the RGB model, but are simply mixed with each other. Behind this layer are blue LEDs. When hit by light from the diode, the quantum dots begin to emit their red and green colors. And just in the process of mixing all three colors, the desired source of ideal white light is obtained. This ensures correct color reproduction without distortion of the color spectrum and loss of color intensity.
Thus, the quantum mechanism will solve a number of problems that conventional backlit LCD displays have. Among the main advantages of QD-LED technology are the following:
- Application of an ideal white light source.
- No problems with loss of contrast and brightness. All colors of the light spectrum have the same degree of intensity. No one color dominates the other.
- Increased color realism by more than 50 percent (about a billion shades).
- Color saturation increases by 40 percent.
Advantages of nanocrystals over OLED
OLED displays, the operation of which is based on organic light-emitting diodes, have become the next step in the development of electronics. Compared to conventional liquid crystal displays, OLEDs have a number of advantages:
- image quality does not change depending on the viewing angle;
- no backlight;
- the weight and dimensions of the product are reduced;
- The brightness and contrast of the image increases.
However, despite all the advantages, this technology has a number of disadvantages. For example, OLED displays have a short service life. Blue LEDs have a limited service life of several years of continuous operation. And when they fail, color accuracy is significantly distorted. Image brightness also affects display life and power consumption: the higher the brightness, the shorter the lifespan and the higher the power consumption. But the most significant problem with using organic LEDs is their mass production. This technology requires a complete replacement of equipment and conveyors at manufacturing plants, and this will lead to a significant increase in the cost of products.
The use of quantum dots requires only minor changes and improvements to existing pipelines. This will directly affect the final cost of the displays. In addition, the use of nanocrystals solves the problem of color rendering fragility and energy efficiency. The result is a high-quality image comparable to OLED while being more affordable for purchase. / Read more on our website.
Thus, quantum dots become a new milestone in the development of liquid crystal displays. Although who knows, maybe a new scientific discovery will be just around the corner that will change our current ideas about advanced technologies.
Today we are reviewing the latest monitor - a 27-inch beauty with a curved WQHD screen made using QLED technology. The approximate price of the device is about $500. This monitor was presented by the manufacturer at the exhibition and it is not yet officially sold in our area. But a test sample has already arrived at the Root Nation editorial office, thanks to which we can be one of the first to become familiar with the technology of quantum dot displays. And of course, I will now tell you in detail about my impressions of this monitor.
Samsung CH711 - monitor with quantum dot displayDesign, materials, assembly Samsung CH711
First, let's talk about beauty. And she is undoubtedly here. The monitor looks elegant and futuristic, which is quite in the spirit of Samsung, which now claims to be the manufacturer of the most advanced, stylish and technologically advanced gadgets. What is encouraging is that this trend does not bypass the company’s monitor segment.
Samsung CH711 monitor with curved QLED panel Samsung CH711 has a frameless design and when turned off, it seems that the display occupies the entire width of the front area. In fact, this is not the case, which becomes clear after turning on the monitor. On the sides and top, the display matrix has a thin black field 5 mm wide. But if there is an image on the screen with a black background around the edges, then the frames completely merge with the image. This effect is achieved thanks to the excellent contrast and deep blacks that the QLED display demonstrates. In any case, there is no massive plastic around the screen - only a neat 12 mm high field with the manufacturer's logo below the screen. The entire remaining area of the front of the monitor is occupied by a directly curved display.
The display matrix is framed at the ends with high-quality gray-silver plastic, and all other elements (back panel and stand) are made of white glossy plastic. But the gloss is moderate - not to a mirror shine. In addition, white plastic does not collect fingerprints and dust on it is almost invisible. In principle, the materials are pleasant and overall the monitor looks good.
The monitor style is discreet minimalism with simple forms. White color is universal and fits any interior style. The curvature of the display emphasizes its compliance with modern technological trends. The quality of materials and build of the monitor is excellent, I have no complaints. In general, Samsung CH711, as an interior element, will undoubtedly decorate any home or office.
Samsung CH711 Quantum Dot Display Layout of elements
In this regard, the Samsung CH711 monitor is very unusual. It uses an original solution where all connection interfaces and cables are hidden under removable covers of the case and stand. Thus, the manufacturer achieved a complete absence of wires hanging from the back, which further improved the appearance of the monitor.
Power and video interface cables are branded and included. They are also white and quite thin, they go inside the legs of the stand and connect to the connectors located in the recess on the case. This area is covered with a removable plug.
There are relatively few connection ports: only a coaxial power connector and 2 options for connecting to the signal source: HDMI or miniDisplayPort. The monitor's power supply is external, also white. Here's what it looks like in practice:
Samsung CH711 display features
The monitor produces a really good picture. But at first glance, I didn’t notice any particular advantage over IPS. Only over time do you begin to notice the excellent contrast of the picture and excellent natural color rendition. There are also no complaints about the viewing angles - they are maximum.
In addition, we can note the high pixel density of the screen. The 2560x1440 resolution is perfect for a 27-inch QLED panel. Fonts look sharp, as do icons and other small elements that Windows abounds in. In addition, when using the Samsung CH711, you don’t have to change the interface display scale - working at 100% is quite comfortable.
A separate point worth talking about is the curvature of the display. Previously, I did not attach importance to this feature and considered it insignificant when choosing a monitor. But after getting used to the curved screen, images on a regular flat monitor begin to appear convex. This is noticeable on rectangular elements that become oval.
Samsung CH711 performs well in any use model - office and text work, photo and video editing, browsing, watching videos and movies.
Separately, I would like to note the gaming orientation of the monitor. Samsung CH711 can be called a gaming monitor, thanks to the low matrix response time (4 ms) and support for .
AMD FreeSync eliminates tearing and stuttering in game images by synchronizing the video frame rate generated by the video accelerator with the monitor's refresh rate, and also compensates for low fps in games running at 30 fps or less.
But I also discovered some problems with the QLED panel. This may be due to the fact that I have an early engineering sample on test and this shortcoming will be eliminated in consumer devices that will go to points of sale.
The essence of the problem is as follows. On solid dark gray objects, I noticed areas of uneven illumination that created a blotchy effect on the screen. This effect is hardly noticeable and is observed precisely on a dark gray background, but I still saw it.
I don't fully understand what this is connected with. Perhaps individual pixels have different backlight levels. Or is it a memory effect (which is most likely) since it seemed to me that there were afterimages on the border of the closed window in which I had been working for a long time before. When transferring a window with a dark gray fill to a second monitor (PLS matrix), this effect was not observed; the color fill was uniform.
Ergonomics and controls
As for adjusting the position of the screen in space, its range is not wide and the possibilities are limited only by tilting the display away from you or towards you.
The monitor has one control element - a multifunction joystick button on the bottom of the display. Using it, you can turn the device on and off, as well as call up the menu and navigate and adjust the monitor. Unfortunately, in my test copy the menu was in Korean, so I wasn’t able to go deeper into the settings. I also couldn’t find a language choice in the menu at random; perhaps the engineering sample simply doesn’t have this option.
Monitor Samsung CH711 - management Next to the button there is a blue monitor operation indicator, which has three states - on, off, standby mode (blinking).
conclusions
Samsung CH711 is an interesting universal monitor that is suitable for use both at home and in the office. Thanks to its exquisite design, it will decorate any room. Using a curved screen is pleasant and convenient in any setting, be it office use, graphic editors, multimedia or games.
Overall, I liked the display made using quantum dot technology - the picture quality is excellent. But perhaps at this stage QLED panels still have some shortcomings and require further development and improvement. In addition, the cost of such monitors is still quite high. However, I am confident that Samsung will succeed, because we know how the company knows how to achieve its goals. I hope that over time more and more consumers will be able to enjoy high-quality images on new monitors from this manufacturer.
