IN recent times OLED displays are becoming increasingly popular among mobile manufacturers. What are the advantages and disadvantages compared to LCD?
Now mobile devices come with different types of displays: LCD, OLED,. Each mobile manufacturer extols the merits of the screen used, and some even improve screen technologies and develop their own options, for example, Super AMOLED from Samsung or Optic AMOLED from OnePlus.
Before buying another “smartphone with the most best display”, You need to figure out how you will benefit from it as a user.
What is OLED?
OLED stands for Organic Light emitting Diode, that is, organic light-emitting diode, or simply organic light-emitting diode. To create them, thin films are used, consisting of several layers of carbon material.
As the name suggests, these diodes emit light as they pass through them. electric current... This is one of the main differences between such displays and liquid crystal screens - they do not need additional backlighting.
The ability of organic materials to glow when exposed to electric current was discovered back in the 1950s. But the technology began to develop rapidly and be applied in various fields only in recent years.
Principle of operation
The LED panel consists of six layers. There are layers at the top and bottom protective glass or plastic. Moreover, the upper layer is called insulating, and the lower one is called a substrate. Since OLEDs are very sensitive to oxygen and moisture, they play an important role.
Between these layers is the cathode (negative electrode) and the anode (positive electrode). And between them, two layers of organic molecules are already placed, which are called emitting (near the cathode, a glow is formed in it) and conductive (near the anode).
To make the LEDs emit light, a voltage is applied across the anode and cathode.
As electricity arrives, the cathode receives electrons from the power source, and the anode loses them, or, in other words, gets holes.
As a result, the electrons make the emitting layer negatively charged, and the conductive layer becomes positively charged.
Positive holes are much more mobile than negative electrons, so they jump over the boundary of the conducting layer to the emitting one. When a hole meets an electron, they cancel each other out, and a short burst of energy is released in the form of a particle of light - a photon.
This process is called recombination. Since it occurs many times per second, the LED produces continuous light until the current stops flowing. Through the use of many red, green and of blue color complex high-resolution color images are obtained.
OLED types
There are two types of LEDs. Traditionally, small organic molecules are placed on glass to produce light. Another type uses large polymer molecules. They are called Light Emitting Polymers (LEP) or Polymer LEDs (PLED) and are thinner and less flexible.
OLED displays can be built different ways... In some designs, light exits through the top insulating layer, in others through the backing. Panels big size also differ in that the pixels are formed from individual LED elements.
The arrangement of red, blue and green pixels can also differ: they can be next to each other or on top of each other. In the latter case, more pixels fit in each square centimeter, which provides more a high resolutionbut the display is also thicker.
OLED benefits
OLED displays are superior to LCDs in many ways.
- Small thickness (about 0.2-0.3 mm, usually LCD is about 10 times thicker).
- Little weight.
- Flexibility.
- High brightness.
- Less power consumption (since no backlight is required).
- High refresh rate (OLED responds 200 times faster, which is important when playing fast moving images, such as watching sports or games).
- More natural colors and richer blacks (due to no black pixel backlighting).
- Wide viewing angle.
Disadvantages of OLED
The biggest disadvantage of OLED displays is their fragility. Early versions of these screens wore out about four times faster than LCDs. With development modern technologies manufacturers have managed to reduce this difference and OLED displays can now withstand years of heavy use.
In addition, as practice shows, red and green diodes last longer than their blue counterparts. Over time, this can lead to color distortion.
Another problem is water sensitivity. As noted above, for this reason, the insulating layer plays an important role here.
It is also worth noting that OLED displays are still more expensive to manufacture than LCDs. As a result, the consumer will have to pay more for a device with an LED panel than for its counterpart with an LCD screen. If the display is damaged, repairs can also be more expensive.
Application
The technology is still relatively new, although more and more manufacturers are looking to use it in own products... Now OLED displays are used in TV screens, computers, iPods, smart watches and smartphones.
OLED (organic light emitting diode) is called the future of television technology, which promises rich colors, including deep blacks, and reduced motion blur.
It may seem that new technology does not differ much from the more common LED panels on the market. But the word "organic" implies a difference in the way images are presented on the screen.
What are the advantages of OLED screens?
LED screen - liquid crystal display with improved lED backlight... In modern LCD TVs, liquid crystals rotate under the influence of electricity and transmit light through every pixel in the image. Light passes through filters (red, blue and green) and when mixed, results in colors ranging from darkest to whites. If all crystals are rotated so as not to miss any of the three colors, then the output is black.
Crystals have their own advantages: low cost, thinness and lightness of materials, but there is also an important disadvantage - the level of black color. The crystals block the light, but the backlight continues to work. Light falls on the “black” pixels, which makes a dark image appear faded.
OLED screens do not - each individual pixel emits light on its own when an electric current is applied to it. If the pixel does not receive electricity, then we see the absence of light - real black.
Absolute zero values \u200b\u200bfor color and brightness alter the perception of contrast. On an OLED display, even the smallest amount of light in the darker parts of the image is perceived brighter than LED displays. In addition, pixels in OLED screens can change color almost instantly, as opposed to lag on LED panels, which take longer to activate and move the crystals.
Another advantage of OLED technology, which derives from the black level and contrast, is realistic saturated colors.
Do pixels burn out on OLED screens?
On old plasma TVs could burn out pixels in those parts of the screen where something static was located for a long time, for example, a channel logo or a video game menu. Traces from such objects could be permanently "imprinted" on the display, so manufacturers added special tools to the TV settings to avoid this.
This is not typical for OLED screens, but if a static image is left for several hours in a row, then it can "freeze", leaving a barely noticeable mark, for about an hour, and then completely disappear. Nothing bad will happen to the TV.
How bright are OLED displays?
If there is an Ultra HD Premium sticker on it, then its pixels must reach the minimum brightness threshold. This value can vary depending on the depth of the black. If the black level in an OLED panel is somewhere between 0.0005 and 0.5 cd / m 2, then the maximum brightness for such a TV should start from 1000 cd / m 2. But if the screen is capable of an even darker color, then its maximum can start from 540 cd / m 2.
The brightness of an OLED TV is perceived depending on where you place it, so in a bright room, the benefits of an OLED screen won't be much noticeable. Inexpensive OLED-panels produce brightness at the level of 700-800 cd / m 2, while LED-TVs are capable of more - 1,400-1,500 cd / m 2.
New models of OLED TVs with brightness up to 2,000 cd / m2 will appear this year, but their price is unlikely to please buyers.
With a maximum screen brightness of 800 cd / m2, its advantages over LCD TVs are noticeable at night when weak light or during the day with the curtains closed. As soon as you dim the light, the effect of black on image quality becomes obvious.
However, deep blacks are not the magic that transforms any movie on screen. Sometimes, for example in streaming services, black can be encoded not as a complete absence of light, but as a lighter version of it.
What are the disadvantages of OLED technology?
As with color rendering quality, motion blur reduction depends on the original content. In theory, OLED technology surpasses LCD and LED standards for motion transmission.
In practice, only specially prepared files and blur reduction mode produce noticeable results. Dynamic movies with an image rate of 24 frames per second will not work. At the same time, it is quite difficult to find 4K video, with realistic colors and high frame rates at the same time, to justify the purchase of an expensive OLED panel.
Should I buy an OLED TV or not?
So far, for most buyers, the answer is no. If you don't need the mandatory HDR-10 or Dolby Vision support, then you can spend much less on a 4K LED TV with low blur and low input lag. You will not get the most juicy picture, but you can, for example, get a good audio system.
If you still want to join the world, then in this case it is better to choose an OLED screen, but you have to properly calibrate it. For large rooms, these TVs are not profitable to buy unless you have more than $ 20,000 for a 77-inch LG model.
The low blur and vibrant colors of OLED panels are also good for gaming, but consider the higher input latency, which affects responsiveness and is especially critical in online gaming. Manufacturers have already begun to solve this problem with firmware updates.
HDR and OLED technologies will surprise you with image quality right now, but there is still little content suitable for them.
OLED is an abbreviation used for high-end TVs. Therefore, it is important for home entertainment lovers to know exactly what it means. This technology represents the next stage in the development of visual display devices, which has finally reached a cost when the average consumer can afford it. She offers best quality images (deeper blacks and brighter whites), lower power consumption and faster response times than traditional TVs.
Market restrictions
So why doesn't everyone know what it is? OLED TVs are prohibitively expensive and for a very long time only two companies, LG and Panasonic, have used this technology in their panels. Fortunately, things are changing today. Sony is one of the first developers of this technology, in 2017 it returned to the game with new version the Bravia A1E TV signal receiver.
So what are OLED TVs? Do they justify their cost? And what are their benefits?
What's the difference between OLED and LCD / LED?
In everything. Although the abbreviations are almost the same, they have completely different image creation processes.
What is OLED TV? This is a matrix of organic light emitting diodes... The organic part refers to the carbon film that sits inside the panel in front of the glass screen. OLEDs emit their own light when electrically charged, and LCD cells require an external source, such as backlighting, to provide brightness. This distinguishes LCD screens from their LED variants. A traditional LCD has a backlight (cold cathode fluorescent light or CCFL) that is uniform across the entire back of the screen.
So to create black or white image lighting of the same brightness is used. This reduces the number of "hot spots" or areas of super-bright light. After all, the actual source illuminating them is homogeneous.
Several years ago, engineers from companies such as Samsung and Sony introduced an LED matrix as a backlight. If a certain part of the screen is black, then the LEDs behind it can be turned off to make it appear darker.
it the best solutionthan CCFL. But it still has its drawbacks. Because it is behind the LCD, the backlight is not fully synchronized with the pixel in front of it. The result is an effect called "halo". When it occurs, the emission of LEDs from the bright areas of the image penetrates into the dark areas.
This is what differentiates OLEDs from LED-backlit LCDs. Their pixels are themselves light sources. So when they need to be black, they can be turned off completely without relying on background lighting.
Image quality
As a result, blacks appear unusually dark, and when this is combined with the brightness of white OLED panels that can only be achieved, the image is fantastically bright and contrasting.
Virtually the only sequential OLED TV makers on the planet, LG and Panasonic, like to use the term “infinite contrast” to describe how auto-adjusting pixels are completely turned off when reproducing blacks, providing “absolute” rather than “relative” depth. It only describes how much darker one pixel can be compared to the brightest area on the screen.
For years, the durability of OLED panels has been questioned, and production lines have not been profitable due to high failure rates. But as companies like LG have invested huge amounts of money in the technology, it has become more affordable, albeit still much more expensive than competing solutions.
Update frequency
The benefits of OLED go beyond simple static image quality thanks to the responsiveness and smoothness of the display itself. This means that OLED gamers and home theater enthusiasts will definitely love it. LED screen Supports refresh rates of up to 0.001ms, which is about 1,000 times faster than a standard LED-backlit LCD panel, and outperforms plasma technology not used today.
Other benefits
And since the light source they are using has become tiny, the depth of the screen has decreased accordingly. This means OLED TVs have unusually deep blacks and bright white peaks, improved color reproduction, and smooth display of motion - all in a form factor that is just a few millimeters deep.
The viewing angles of OLED screens are excellent. Even when viewed from a wide angle, images remain consistent, colors are vibrant and contrast is brilliant.
AMOLED vs OLED
IN cell phones and others portable devices often used aMOLED screens... AM stands here for "active matrix" and represents a way of addressing the display by the electronics of the device. It is just another way to launch an OLED screen, which is better for conveying motion (like video). Each pixel they have can be addressed individually, which is required in the TV.
Active matrix LCD monitors were called TFT LCDs. Today, this is not particularly indicated, because every manufactured liquid crystal display of a phone, tablet, TV, etc. is equipped with an active matrix. The same idea is inherent in LED panels. OLED TVs are a kind of active matrix.
What OLED TVs are currently being produced?
OLED panels entered the market in 2012 and have been manufactured by various manufacturers for many years. Previously, OLED screens were only produced by Samsung and LG. But the first of these South Korean companies ditched the idea due to the high cost and complexity of the technology, and is not going to reopen production anytime soon.
LG OLED TVs have been steadily released over the past few years. In 2016, the company introduced 4 product lines with OLED panels - G6, E6, C6 and B6. And in 2017 she released 5 models - G7, E7, C7, B7 and completely new tv LG OLED 65 ”W7 with an incredibly thin screen and Dolby Atmos soundbar.
Fortunately, LG is not entirely alone in the market today. Panasonic released its first OLED kit, the TX-65CZ950, and continued with impressive model range other TVs.
Last but not least, Sony's new (or old?) Rival is the Bravia A1E, which looks incredible.
Can OLED play 3D?
3D may have lost its appeal as a television feature, but that doesn't stop manufacturers from continuing to include support for it in their high-end models.
LG and Panasonic have included 3D as a feature on their 2016 OLED TVs. And in most cases it's the passive variation, which means cheaper glasses and less screen flicker.
The disadvantage of passive 3D is the drop in resolution. But fortunately, almost all OLED kits now come with a UHD display that has enough pixels to avoid any discomfort. LG's 2017 OLED TVs do not support 3D, but this is unlikely to disappoint many.
The price of new technology
LED screens are definitely getting cheaper, but they are still difficult to call affordable. The cheapest LG OLED TVs are priced at $ 1,800. Panasonic technology will cost even more.
The paucity of OLED TVs on the market means that a small number of manufacturers are more or less free to set the price they want. No drop in value is expected until more competitors emerge.
However, usually, when one company starts moving forward, the others quickly catch up. Prices should come down as manufacturers solve production line problems and demand for this phenomenal technology rises.
Perspective
Today, it is already clear that OLED TVs are a technology that, even after several years of intensive development, is still quite complex and expensive for manufacturers. The fact that it has existed for so long and still has not reached the level of mass production makes many people think that it has no future.
It is quite obvious that the companies still haven't given up on OLED. This means the opposite. Technology is far from being forgotten. But after so many years of trying to get it to work effectively, it’s hard to maintain hope that it will ever become truly affordable.
Chances of success
However, the high cost of OLED does not mean that manufacturers are unable to improve it. The $ 1,800 price tag cannot be called a budget price, let alone $ 8,000 for the 65 "LG OLED65W7 OLED TV, but it is much cheaper than the cost of this type of display, which was just a few years ago. If this trend continues, then one can hope that in a couple of years the technology will become dominant. Although it still remains the lot of a few enthusiasts.
Organic LED (eng. Organic Light-Emitting Diode (OLED) - organic light-emitting diode) - a semiconductor device made of organic compounds that effectively emit light when an electric current is passed through them. OLED technology is mainly used in the creation of information display devices (displays). It is expected that the manufacture of such displays will be much cheaper than the manufacture of liquid crystal displays.
1.5-inch OLED display
Operating principle
To create organic light-emitting diodes (OLED), thin-film multilayer structures are used, consisting of layers of several polymers. When a positive voltage is applied to the anode, the flow of electrons flows through the device from the cathode to the anode. Thus, the cathode donates electrons to the emission layer, and the anode picks up electrons from the conducting layer, or in other words, the anode donates holes to the conducting layer. The emission layer is negatively charged and the conductive layer is positive. Under the influence of electrostatic forces, electrons and holes move towards each other and recombine when they meet. This happens closer to the emission layer, because holes in organic semiconductors have a higher mobility than electrons. During recombination, a decrease in the electron energy occurs, which is accompanied by the release (emission) electromagnetic radiation in the field of visible light. Therefore, the layer is called emission.
Scheme of a 2-layer OLED panel: 1. Cathode (-), 2. Emission layer, 3. Emitted radiation, 4. Conductive layer, 5. Anode (+)
The device does not work when a negative voltage is applied to the anode. In this case, holes move to the anode, while electrons move in the opposite direction to the cathode, and no recombination occurs.
Indium oxide doped with tin is usually used as the anode material. It is transparent to visible light and has a high work function that facilitates the injection of holes into the polymer layer. Metals such as aluminum and calcium are often used for the manufacture of the cathode, since they have a low work function, which facilitates the injection of electrons into the polymer layer.
Benefits Compared to Plasma Displays
- smaller dimensions and weight
Advantages Compared to LCD Displays
- smaller dimensions and weight
- no need for backlighting
- lack of such a parameter as viewing angle - the image is visible without loss of quality from any angle
- better color rendering (high contrast)
- lower power consumption at the same brightness
- the ability to create flexible screens
Brightness... OLED displays provide radiation brightness from a few cd / m2 (for night work) to very high brightness - over 100,000 cd / m2, and their brightness can be adjusted in a very wide dynamic range... Since the display life is inversely proportional to its brightness, it is recommended for instruments to operate at more moderate brightness levels up to 1000 cd / m2. When the LCD is illuminated with a bright beam of light, glare appears, and the picture on the OLED screen will remain bright and saturated in any light level (even with direct sunlight on the display).
Contrast. OLED is also the leader here. OLED displays have a contrast ratio of 1,000,000: 1 (LCD contrast 1300: 1, CRT 2000: 1)
Viewing angles. OLED technology allows you to look at the display from any side and from any angle, without losing image quality.
Energy consumption. Quite low power consumption - about 25W (LCD has 25-40W). The efficiency of an OLED display is close to 100%, that of an LCD is -90%. The power consumption of PHOLED is even lower.
The demand for the benefits of organic displays is growing every year. This fact allows us to conclude that soon humanity will see the flowering of this technology.
History
André Bernanose and his collaborators discovered electroluminescence in organic materials in the early 1950s by applying high voltage alternating current to transparent thin films of acridine orange and quinacrine dye. In 1960, researchers at the Dow Chemical Company developed controlled alternating current electroluminescent cells using doped anthracene.
The low electrical conductivity of such materials limited the development of technology until more modern organic materials such as polyacetylene and polypyrrole became available. In a number of articles that year, scientists reported that they had observed high conductivity in iodine-doped polypyrrole. They reached a conductivity of 1 S / cm. Unfortunately, this discovery was "lost". And only in a year, the properties of a bistable switch based on melanin with high conductivity in the "on" state were investigated. This material emitted a flash of light when turned on.
Volume of sales
The OLED display market is slowly but surely growing. Thus, from April to June 2007, sales growth was + 4%, having added 24% over the year, and reached $ 123.4 million (Sales volume in the year was ~ $ 85 million).
Some analysts estimate the organic display market will grow to $ 3.7 billion by 2010. In 2008, OLED production is projected to increase to 18,000 units per month. In 2009, the volume of output will increase to 50 thousand, and by 2010 - up to 120 thousand per month.
Development prospects and fields of application
Today OLED technology is used by many narrowly focused developers, for example, to create night vision devices. OLED displays are embedded in phones, digital cameras and other techniques where a large full color screen is not required. There are also monitors based on organic matter, for example Samsung is actively developing in this area (the 40-inch limit has been reached). And Epson released a 40-inch display back in 2004. The success can be explained by the fact that the production technology of such displays is similar to the printing technology in inkjet printer, and in this business the company has a lot of experience.
Recent achievements
Sony Development
Other companies
The Nokia N85 smartphone, announced in August 2008 and going on sale in October 2008, is the first smartphone from the Finnish company with an AM-OLED display, not a very expensive all-in-one device.
Optimus Maximus keyboard (Lebedev Studio), released in early 2008 using 48x48 pixel OLED displays (10.1x10.1mm) for keys.
OLED can be used in high resolution holography (Volumetric display). Professor Orbit showed a 3D video on May 12, 2007 at EXPO Lisbon (potential uses of these materials).
OLEDs can also be used as light sources. OLED's efficiency and runtime already exceed those of lamps. OLEDs are used as a general lighting source (EU - OLLA project).
On March 11, 2008, General Electric (GE Global Research) demonstrated the first successful roll-to-roll OLED as a major success on the road to cost-effective commercial OLED technology. The 4-year research project cost $ 13 million (Energy Conversion Devices, Inc and National Institute of American Trade Standards and Technology (NIST), GE Global Research).
Chi Mei EL Corp of Tainan, Inc., showcased 25 "(inch) low temperature transparent silicon Active Matrix OLEDs at the Society of Information Displays (SID) at a conference in Los Angeles, USA May 20-22, 2008.
OLED displays in mobile devices are becoming more and more popular. They were once used mainly by Samsung's flagship models, but now this technology is used in both cheaper Galaxy and smartphones from other manufacturers, for example, Meizu, Xiaomi, Huawei, Lenovo and OnePlus. Numerous rumors indicate that the next top-of-the-line iPhone will receive an OLED panel for the first time in the brand's history. Both IPS LCD and AMOLED displays are now used in both inexpensive and flagship models... What is the reason for the popularity of OLED, which is growing more and more?
For those who do not yet know how they differ OLED- and LCD displays, we have prepared this article. Both technologies have their advantages and disadvantages, and when choosing smartphone it is worth considering which panel is installed under its protective glass.
The screen is perhaps the main component of any modern smartphone. We make voice calls less and less, but more and more we use our pocket devices for surfing the net, taking photos and videos, as well as communicating in instant messengers. That is, we look at the screen of a mobile phone almost all the time when it is in our hands.
LCD (Liquid Crystal Display)
Liquid crystal screens were invented many years ago. LCD panels use liquid crystal light, which is also backlit by a separate system of small lamps. LCD screens are installed in computer monitors, TVs, cameras and many other devices.
Smartphones use two types of LCD panels - TFT LCD and IPS LCD. The first ones are found less and less often - they are inferior to LCDs in all respects except for cost.
IPS LCDs consume little power and behave well in the sun. The first and, perhaps, the main difference from OLED, which immediately catches the eye when compared, is a noticeably lower contrast level. As a result, blacks on an LCD screen will be lighter and paler than on an OLED screen.
LCD wins in terms of more accurate shade display, but quite often manufacturers do not calibrate the screens of their devices well. As a result, the display may display a very pale red or very pale blue tint instead of pure white.
It is worth noting that smartphones with QLED-type LCD screens may appear on the market in the future. These screens are slightly thicker due to the additional layer that distinguishes them from LCDs, but they look much more attractive. For their use in small mobile deviceshowever, there are many more challenges that engineers have to solve.
OLED (Organic Light-Emitting Diode, organic light emitting diode)
OLED displays use a special type of LED that emits much more light and does not need separate system backlight. This makes the dark areas of the screen appear much more pronounced and deeper, and the light areas appear richer and brighter in comparison.
Plus, the lack of backlighting makes OLEDs thinner than LCDs - they don't have a whole layer that illuminates the pixels.
OLED screens also fall into two categories - PMOLED and AMOLED. Basically, we only hear about the latter, since PMOLED is not used in smartphones, TVs and other expensive mainstream devices.
PMOLED panels are very cheap because they use passive matrices, but are not suitable for displaying complex pictures. Now PMOLED screens can be found, for example, in inexpensive fitness trackers. Such panels cannot be larger than three inches diagonally.
AMOLED (OLED with active matrix)
AMOLED panels are similar to PMOLEDs, but differ in the use of an active matrix, so they do an excellent job of displaying complex pictures and quickly changing them. There are no size restrictions for AMOLED screens - they are used as in smart watch (for example, in Apple Watch), and in huge TVs with a diagonal of several tens of inches.
The two main disadvantages of AMOLED are the increased battery consumption in many cases and not too high brightness in lighting conditions. sunbeams.
AMOLED panels consume more energy precisely due to the fact that each microscopic diode illuminates itself. As we have seen, this has many benefits, but it also means that a bright picture (like a photo of a sunlit garden) requires more current than an LCD. Many apps even have dedicated OLED modes that show as much black as possible on the screen to save battery power.
In addition, over time, AMOLED displays degrade faster than LCDs, and the rate of deterioration of quality will vary from area to area. A few years ago, pixel burnout was a huge problem - after a long time, pale, but clearly visible interface elements remained on the device screen forever operating system... In the most modern smartphones Samsung and other companies use several tricks to solve this problem. For example, in the Galaxy S8, the position of the on-screen Android navigation buttons is constantly shifted by a few pixels - the user will not notice this, and there will be no traces of them on the screen even after several years.
Conclusion
In most comparisons, AMOLED displays win out, and there is no point in arguing with this fact. The colors are more saturated, the contrast is much deeper, and the response speed is faster. But the LCD also has its trump cards - better readability in direct sunlight (however, the difference with modern AMOLEDs is almost leveled here), as well as a more accurate display of shades.
At the same time, it should be understood that the final image quality depends not only on the screen production technology, but also on calibration, as well as simply on the quality of the matrix. As a result, the best way out of the situation (if you want to buy a smartphone with the best display on the market or in a specific price range) is to read specialized reviews that focus specifically on color quality, brightness and contrast. The choice between AMOLED and IPS LCD should be made at the very beginning.
Most likely, in the future, more and more expensive mobile phones will use AMOLED, and IPS LCD will become a budget solution and replace TFT LCD. Perhaps the iPhone's transition to a new type of bezel will push the industry even further. It is because of him that several companies (for example, LG) have recently begun to invest many millions of dollars in factories for the production of OLED screens.
