How OLEDs (organic LEDs) work
Photo: LEDs on an electronic instrument panel. They make light by the controlled movement of electrons, not by heating up a wire filament. That's why LEDs use much less energy than conventional lamps.
An OLED is simply an LED where the light is produced ("emitted") by organic molecules. When people talk about organic things these days, they're usually referring to food and clothing produced in an environmentally friendly way without the use of pesticides. But when it comes to the chemistry of how molecules are made, the word has a completely different meaning. Organic molecules are simply ones based around lines or rings of carbon atoms , including such common things as sugar, gasoline, alcohol, wood , and plastics .
LEDs (light-emitting diodes) are the tiny, colored, indicator lights you see on electronic instrument panels. They're much smaller, more energy -efficient, and more reliable than old-style incandescent lamps . Instead of making light by heating a wire filament till it glows white hot (which is how a normal lamp works), they give off light when electrons zap through the specially treated ("doped") solid materials from which they're made.
Do you remember old-style TVs powered by cathode-ray tubes (CRTs)? The biggest ones were about 30–60cm (1–2ft) deep and almost too heavy to lift by yourself. If you think that's bad, you should have seen what TVs were like in the 1940s. The CRTs inside were so long that they had to stand upright firing their picture toward the ceiling, with a little mirror at the top to bend it sideways into the room. Watching TV in those days was a bit like staring down the periscope of a submarine ! Thank goodness for progress. Now most of us have computers and TVs with LCD screens , which are thin enough to mount on a wall, and displays light enough to build into portable gadgets like cellphones . But displays made with OLED (organic light-emitting diode) technology are even better. They're super-light, almost paper-thin, theoretically flexible enough to print onto clothing, and they produce a brighter and more colorful picture. What are they and how do they work? Let's take a closer look!
OLEDs work in a similar way to conventional diodes and LEDs, but instead of using layers of n-type and p-type semiconductors, they use organic molecules to produce their electrons and holes. A simple OLED is made up of six different layers. On the top and bottom there are layers of protective glass or plastic . The top layer is called the seal and the bottom layer the substrate. In between those layers, there's a negative terminal (sometimes called the cathode) and a positive terminal (called the anode). Finally, in between the anode and cathode are two layers made from organic molecules called the emissive layer (where the light is produced, which is next to the cathode) and the conductive layer (next to the anode).
An LED is a junction diode with an added feature: it makes light. Every time electrons cross the junction, they nip into holes on the other side, release surplus energy, and give off a quick flash of light. All those flashes produce the dull, continuous glow for which LEDs are famous.
Before you can understand an OLED, it helps if you understand how a conventional LED works—so here's a quick recap. Take two slabs of semiconductor material (something like silicon or germanium), one slightly rich in electrons (called n-type) and one slightly poor in electrons (if you prefer, that's the same as saying it's rich in "holes" where electrons should be, which is called p-type). Join the n-type and p-type slabs together and, where they meet, you get a kind of neutral, no-man's land forming at the junction where surplus electrons and holes cross over and cancel one another out. Now connect electrical contacts to the two slabs and switch on the power. If you wire the contacts one way, electrons flow across the junction from the rich side to the poor, while holes flow the other way, and a current flows across the junction and through your circuit. Wire the contacts the other way and the electrons and holes won't cross over; no current flows at all. What you've made here is called a junction diode: an electronic one-way-street that allows current to flow in one direction only. We explain all this more clearly and in much more detail in our main article on diodes .
We can make an OLED produce colored light by adding a colored filter into our plastic sandwich just beneath the glass or plastic top or bottom layer. If we put thousands of red, green, and blue OLEDs next to one another and switch them on and off independently, they work like the pixels in a conventional LCD screen, so we can produce complex, hi-resolution colored pictures.
Types of OLEDs
There are two different types of OLED. Traditional OLEDs use small organic molecules deposited on glass to produce light. The other type of OLED uses large plastic molecules called polymers. Those OLEDs are called light-emitting polymers (LEPs) or, sometimes, polymer LEDs (PLEDs). Since they're printed onto plastic (often using a modified, high-precision version of an inkjet printer) rather than on glass, they are thinner and more flexible.
Photo: In OLEDs, thin polymers turn electricity into light. Polymers can also work in the opposite way to convert light into electricity, as in polymer solar cells like these. Photo by Jack Dempsey courtesy of US DOE/NREL (US Department of Energy/National Renewable Energy Laboratory).
OLED displays can be built in various different ways. In some designs, light is designed to emerge from the glass seal at the top; others send their light through the substrate at the bottom. Large displays also differ in the way pixels are built up from individual OLED elements. In some, the red, green, and blue pixels are arranged side by side; in others, the pixels are stacked on top of one another so you get more pixels packed into each square centimeter/inch of display and higher resolution (though the display is correspondingly thicker).
Advantages and disadvantages of OLEDs
Photo: TVs, computer monitors, and mobile devices (laptops and tablets) are gradually becoming thinner thanks to OLED technology. Photo courtesy of LG Electronics published on Flickr under a Creative Commons Licence.
OLEDs are superior to LCDs in many ways. Their biggest advantage is that they're much thinner (around 0.2–0.3mm or about 8 thousandths of an inch, compared to LCDs, which are typically at least 10 times thicker) and consequently lighter and much more flexible. They're brighter and need no backlight, so they consume much less energy than LCDs (that translates into longer battery life in portable devices such as cellphones and MP3 players). Where LCDs are relatively slow to refresh (often a problem when it comes to fast-moving pictures such as sports on TV or computer games), OLEDs respond up to 200 times faster. They produce truer colors (and a true black) through a much bigger viewing angle (unlike LCDs, where the colors darken and disappear if you look to one side). Being much simpler, OLEDs should eventually be cheaper to make than LCDs (though being newer and less well-adopted, the technology is currently much more expensive).
As for drawbacks, one widely cited problem is that OLED displays don't last as long: degradation of the organic molecules meant that early versions of OLEDs tended to wear out around four times faster than conventional LCDs or LED displays. Manufacturers have been working hard to address this and it's much less of a problem than it used to be. Another difficulty is that organic molecules in OLEDs are very sensitive to water. Though that shouldn't be a problem for domestic products such as TV sets and home computers, it might present more of a challenge in portable products such as cellphones.
What are OLEDs used for?
Photo: TVs and phones are still the most familiar application of OLEDs—but expect many more things to follow as prices become increasingly competitive with older technologies such as LCD. Photo of a curved LG OLED TV by courtesy of Kārlis Dambrāns published on Flickr under a Creative Commons (CC BY 2.0) Licence.
OLED technology is still relatively new compared to similar, long-established technologies such as LEDs and LCDs (both of which were invented in 1962). Broadly speaking, you can use OLED displays wherever you can use LCDs, in such things as TV and computer screens and MP3 and cellphone displays. Their thinness, greater brightness, and better color reproduction suggests they'll find many other exciting applications in future. They might be used to make inexpensive, animated billboards, for example. Or super-thin pages for electronic books and magazines. How about paintings on your wall you can update from your computer? Tablet computers with folding displays that neatly transform into pocket-sized smartphones? Or even clothes with constantly changing colors and patterns wired to visualizer software running from your iPod!
Samsung started using OLED technology in its TVs back in 2013, and in its Galaxy smartphones the following year. Apple, originally dominant in the smartphone market, has lagged badly behind in OLED technology until quite recently. In 2015, after months of rumors, the hotly anticipated Apple Watch was released with an OLED display. Since it was bonded to high-strength glass, Apple was presumably less interested in the fact that OLEDs are flexible than that they're thinner (allowing room for other components) and consume less power than LCDs, offering significantly longer battery life. In 2017, the iPhone X became the first Apple smartphone with an OLED display.
Photo: Audi, Mercedes Benz, and other car makers now use OLEDs in their car head lights, tail lights, and dash displays. Photo by Nan Palmero published on Wikimedia Commons under a Creative Commons (CC BY 2.0) Licence.
Despite the hype, consumers were originally less enthusiastic about mobiles and TVs with OLED screens, largely because LCDs were much cheaper and a tried and trusted technology. That's no longer true, certainly not of TVs: prices of OLED kit have fallen dramatically, with some OLED TVs on sale in 2020/2021 going for about half the price that they were just a year or two earlier and predictions that the technology would become truly affordable by 2023. Where phones are concerned, the advantages of OLEDs—(arguably) better display quality, improved battery life, lighter weight, and thinness/flexibility—often outweigh any simple cost difference. In a telling 2020 analysis, Ross Young of Display Supply Chain Consultants noted a steady shift from LCD as Asian manufacturers switch production to OLEDs and new technologies such as 5G wireless become increasingly important. Young forecasts that OLEDs will account for just over a half (54.5 percent) of the smartphone display market by 2025, compared to just under a quarter (23.9 percent) in 2016.
Who invented OLEDs?
Organic semiconductors were discovered in the mid-1970s by Alan Heeger, Alan MacDiarmid, and Hideki Shirakawa, who shared the Nobel Prize in Chemistry in 2000 for their work. The first efficient OLED—described as "a novel electroluminescent device... constructed using organic materials as the emitting elements"—was developed by Ching Tang and Steven VanSlyke, then working in the research labs at Eastman Kodak, in 1987. Their work, though novel, built on earlier research into electroluminescence, which was first reported in organic molecules by a French physicist named André Bernanose in 1955. He and his colleagues applied high-voltage AC (alternating current) electric fields to thin films of cellulose and cellophane "doped" with acridine orange (a fluorescent, organic dye) and carbazole. By 1970, Digby Williams and Martin Schadt had managed to create what they called "a simple organic electroluminescent diode" using anthracene, but it wasn't until Tang and VanSlyke's work, in the 1980s, that OLED technology became truly practical.
Milestones in the development of OLEDs since then have included the first commercial OLED (Pioneer, 1997), the first full-sized OLED display (Sony, 2001), the first OLED mobile phone display (Samsung, 2007), commercial OLED lighting systems (Lumiotec, 2013), and large-screen commercial OLED TVs (by Samsung, LG, Panasonic, Sony, and others in 2012 and 2013). [1] In 2020, Chinese manufacturer TCL announced it would invest almost $7 billion in a new method of making OLEDs using a technology similar to inkjet printing, with the promise of producing cheaper OLED products by 2023.
What Is OLED and How Does It Work?
OLED, an advanced form of LED, stands for organic light-emitting diode. Unlike LED, which uses a backlight to provide light to pixels, OLED relies on an organic material made of hydrocarbon chains to emit light when in contact with electricity.
There are several advantages to this approach, particularly the ability for each and every pixel to make light on their own, producing an infinitely high contrast ratio, meaning blacks can be completely black and whites extremely bright.
This is the main reason more and more devices use OLED screens, including smartphones, wearables, TVs, tablets, monitors, and digital cameras. Among those devices and others are two kinds of OLED displays that are controlled in different ways, called active-matrix (AMOLED) and passive-matrix (PMOLED).
pbombaert / Getty Images
How OLED Works
An OLED screen includes a number of components. Within the structure, called the substrate, is a cathode that provides electrons, an anode that "pulls" the electrons, and a middle portion (the organic layer) that separates them.
Inside the middle layer are two additional layers, one responsible for producing the light and the other for catching the light.
The color of the light that's seen on the OLED display is affected by red, green, and blue layers attached to the substrate. When color is to be black, the pixel can be turned off to ensure that no light is generated for that pixel.
This method to create black is very different than the one used with LED. When a to-be black pixel is set to black on an LED screen, the pixel shutter is closed but the backlight is still emitting light, meaning it never quite goes all the way dark.
OLED Pros
When compared to LED and other display technologies, OLED offers these benefits:
Energy efficient since a backlight isn't being powered. When black is used, those specific pixels don't need power at all, further saving energy.
The refresh rate is much faster since pixel shutters aren't used.
With fewer components, the display, and thus the whole device can remain thin and lightweight.
Black color is truly black since those pixels can be shut off completely and there isn't nearby lighting from behind that provides a faint glow in that area. This allows for a really high contrast ratio (i.e., the brightest whites over the darkest blacks).
Supports a wide viewing angle without as much color loss as LED.
The absence of any excess layers allows for curved and bendable displays.
OLED Cons
However, there are also disadvantages to OLED displays:
Since part of the display is organic, OLEDs show color degradation over time, which affects the overall screen brightness and color balance. This gets worse with time since the material required for making blues decays at a quicker rate than reds and greens.
OLED screens are expensive to make, at least compared to older technology.
Both OLED and LED displays experience screen burn-in if particular pixels are used for too long over a long period of time, but the effect is greater on OLEDs. However, this effect is in part determined by the number of pixels per inch.
More Information on OLED
Not all OLED screens are the same; some devices use a specific kind of OLED panel because they have a specific use.
For example, a smartphone that requires a high refresh rate for HD images and other always-changing content might use an AMOLED display. Also, because these displays use a thin-film transistor to switch the pixels on/off to display color, they can even be transparent and flexible, called flexible OLEDs (or FOLED).
On the other hand, a calculator that usually displays the same information on the screen for longer periods than a phone, and that refreshes less often, can utilize a technology that provides power to specific areas of the film until it's refreshed, like PMOLED, where each row of the display is controlled instead of each pixel.
Some other devices that use OLED displays come from manufacturers that produce smartphones and smartwatches, like Samsung, Google, Apple, and Essential Products; digital cameras such as Sony, Panasonic, Nikon, and Fujifilm; tablets from Lenovo, HP, Samsung, and Dell; laptops like Alienware, HP, and Apple; monitors from Oxygen, Sony, and Dell; and televisions from manufacturers like Toshiba, Panasonic, Bank & Olufsen, Sony, and Loewe. Even some car radios and lamps use OLED technology.
What a display is made up of doesn't necessarily describe its resolution. In other words, you can't know what the resolution is of a screen (4K, HD, etc.) just because you know it's OLED (or Super AMOLED, LCD, LED, CRT, etc.).
QLED is a similar term that Samsung uses to describe a panel where LEDs collide with a layer of quantum dots to have the screen light up in various colors. It stands for quantum-dot light-emitting diode.
FAQ
Can you fix burn-in on OLED?
There are a few things you can try to fix burn-in on an OLED screen. For instance, you can adjust brightness settings, check for a screen refresh function, or play a fast-moving, colorful video.
What is the smallest OLED TV?
LG Display announced a new 42-inch OLED panel in 2021. Prior to that, Sony unveiled its 48-inch Master Series A9S, the company’s smallest 4K OLED ever, in 2020.
What is P OLED?
P OLED, sometimes called PLED, is a type of AMOLED (active-matrix OLED). However, P OLED uses a plastic substrate instead of the glass substrate used to make typical AMOLED displays,
PCMonitors.info
Author: Adam Simmons
Last updated: April 15th 2023
What are they?
OLED monitors are flat computer displays which consist of pixels made from OLEDs (Organic Light Emitting Diodes) rather than liquid crystal filled units. Unlike LCD (Liquid Crystal Display) technology, OLED does not require backlighting to function. The principle of this technology is that when current flows between a cathode and an anode, an emissive layer of organic molecules (e.g. polyaniline, green in diagram) sandwiched between these electrodes can become illuminated (electroluminescence). For this to happen efficiently, a layer known as the conductive layer (orange in diagram), made up of organic plastic molecules such as polyfluorene, lies between the emissive layer and the anode. The anode is positively charged and therefore draws electrons from the conductive layer, leaving the conductive layer with a positive charge that draws electrons from the emissive layer. Light is emitted as a by-product, in a process known as electrophosphorescence. The OLED process is explained in the diagram below.
OLED process diagram (credit: HowStuffWorks)
The layers described above total a thickness of around 100-500 nanometres, which is around 100 times thinner than human hair. This makes them extremely fragile and hence they must be supported by an additional substrate layer. This substrate is usually clear plastic, foil or glass of varying thickness, and must be transparent, like the anode, so that the emitted light can be seen on the screen. The layering of an OLED cell can be seen below:
OLED cell diagram (credit: HowStuffWorks)
The colour of light emitted from the emissive layer depends on the exact organic makeup of the molecules within. As with LCD (liquid crystal display), OLED units are made up of ‘pixels’ of different colours; i.e. various organic molecules make up ‘pixels’ within the emissive layer which will emit light of different colours once illuminated. The brightness (light intensity) of an OLED is proportional to the current applied to the cell.
As an Amazon Associate I earn from qualifying purchases made using the below link. Where possible, you’ll be redirected to your nearest store. Further information on supporting our work.
Buy from Amazon
Types of OLED screen
There are several types of OLED cells which are being developed for possible incorporation into OLED monitors. The principles used in all are similar to those explained above, but the arrangement of the layers within the cells and the exact materials used differs slightly. Some technologies described below are not applicable to PC monitors and will be restricted to specialist applications such as heads-up-displays on aircraft or small bright clock screens; but we explore them anyway.
Passive-matrix
Passive-matrix OLED (PMOLED) screens consist of cells with opaque cathodes and transparent anodes laid perpendicular to one another in strips. Between these strips are the organic layers of alternate coloured light-emitting diodes and conductive molecules. Once power is switched on to external circuitry (voltage is applied), current flows through particular cathode and anode strips, so that light of selected colours and brightness are emitted through the electrode intersections according to the molecules illuminated and current applied (respectively). The PMOLED process is shown diagrammatically below, with only two pixel colours shown for simplicity:
PMOLED cell (credit: HowStuffWorks)
Active-matrix
Active-matrix OLED (AMOLED) screens are currently receiving massive research and development funds from the likes of Samsung, LG and Sony for incorporation into HDTVs and PC monitors. AMOLED cells contain organic molecule layers and anodes arranged in small sheets (pixels), sandwiched between a larger cathode sheet and integrated into a TFT (thin film transistor) matrix. The TFT matrix not only acts as the supporting substrate; it also controls which pixels become activated by switching on or off current flow to the appropriate pixels and hence drives them in a similar manner to TFT LCD monitors. The typical layout of such a cell is shown below, again with only two pixel colours for diagrammatic purposes. Note that the cell featured in the diagram is bottom-emitting (i.e. has a transparent TFT backplane that light passes through). AMOLED cells may also be top-emitting, meaning that light passes through a transparent cathode rather than the substrate (TFT backplane), which is reflective or transparent.
AMOLED cell (credit: HowStuffWorks)
Because TFT matrices are more efficient than the external circuits of PMOLED displays, AMOLED is extremely energy efficient in comparison. The TFT array controls current very rapidly and accurately, and is not held back by liquid crystals; Active Matrix OLED screens therefore have exceptional response times and colour reproduction.
Other OLED technologies
Although AMOLED is potentially useful for monitors and TVs, there are several additional technologies which have rather particular specialist applications. Transparent OLEDs (TOLEDs) make use of a transparent cathode in addition to the already transparent anode and substrate to produce a screen that is over 80% as transparent as the substrate used, when the pixels are in the off state. Although this could potentially be used in high-end displays (that you can literally see through), this application is limited by the inability of the TOLED matrix to display ‘black’. Nonetheness; this has particularly interesting applications in the military in aircraft, vehicle and soldier-mounted HUDs (heads-up displays).
By using a highly flexible substrate, such as thin foils or plastics, it is also possible to make a durable, lightweight and even foldable OLED screen (FOLED). These have interesting applications for both civilians and military personnel, as they have be integrated into clothing. Another emerging technology involves the use of ‘pure’ white OLEDs as an efficient lighting alternative. The light emitted is more energy-efficient, brighter and whiter than fluorescent or incandescent light bulbs. By producing OLEDs in large sheets, which is an advantage of the current ‘printing’ manufacturing process, it is possible to make large thin sheets of light for use on walls and ceilings. It is even possible to make them transparent so that they could act as windows during the day and lights during the evening – perhaps even allowing them to black out.
The advantages
In 2009 and into 2010, a great drive has been made by PC monitor and TV manufacturers (in particular LG and Samsung) to replace the usual CCFL (Cold Cathode Fluorescent Lamp) backlights of LCD monitors with LED backlights using either white or coloured arrays. The predominant modern form of this backlight uses strips or clusters of white LEDs behind the edges of a monitor – a backlight typed dubbed WLED. A WLED backlight is lighter, thinner and more efficient than a CCFL-backlight but have until recently been very limited in their colour gamut output.
OLED technology is the next step in the evolution of the display, as it does away with the backlight entirely. With only a thin transparent film in the way of the light emitted by the pixels, you get an image with previously impossible contrast, greater apparent brightness and vivid, lifelike colours with an exceptionally wide gamut. Response times and refresh rates are also significantly enhanced over even the best LCDs – an OLED monitor could theoretically have a response time of around 0.01ms and a refresh rate exceeding 1KHz (1000Hz). Manufacturers are also experimenting with multiple emissive layers to enhance the brightness, which is possible due to the exceptionally thin nature of the cells. The end result of all this is images that are much more vivid and lifelike than anything produced by an LCD. No picture or video could ever do these changes justice but this one gets the point across quite nicely.
OLED image quality
Not only is the hypothetical OLED monitor exceptionally thin and light, by doing away with the backlight you also save a tremendous amount of power; when these hit the mass-market they could be over 10 times as efficient as the best LED-backlit LCD monitor of today. As the technology stands at the moment they are considerably more efficient than LCD screens of comparable size when displaying mainly blacks and dark colours – but a lot of white on screen drives current power consumption up significantly. One undeniable advantage of is viewing angles that are vastly superior to any LCD display; light is emitted directly from the emissive layers of OLED displays. LCDs of any panel type have varying degrees of contrast and colour shift to the picture which increases at steeper viewing angles. Even IPS-type panels, the strongest performers in LCD form, show shifts which OLED panels are free from.
Although not necessarily widely applicable to larger screens, OLEDs can also be flexible and/or transparent. This allows them to be used for certain specialist applications as explored in the previous section.
The disadvantages
The largest problem facing manufacturers is that organic materials used in OLED displays degrade over time, like any organic matter. The most troublesome element of this degradation is that blue-emissive pixels degrade more rapidly than their red and green counterparts. This could potentially lead to colour balance issues over time and is of great concern for PC monitors due to how frequently they would be used (unlike a small smartphone screen, for example, which spends most of its time on standby). There are also concerns over image retention. This is where static content is displayed for an extended period of time and can be seen as an ‘afterimage’ for a while even when the content displayed should have changed. For frequently changing content (i.e. TV viewing) this isn’t generally of such concern, but for PC usage it certainly is.
Advancements in OLED
Great strides have been made by Samsung and partners to increase the lifetime of OLED pixels of all colours. By using improved technology to ‘spray’ organic materials onto the substrate surface and by using slightly different molecules, it is thought that the lifetime of ‘blue’ pixels could be extended from 14,000 hours to 60,000 hours (nearly 7 years). This would mean that all pixel colours would degrade at similar rates and would give the monitor a useful life of several years. This same spraying process should reduce manufacturing costs (a large problem for OLED screens today) by reducing wasted materials and the completion of important and expensive research. A recent ‘spraying’ process referred to as ‘solution coating technology’ has been developed by DuPont and is showing great improvements in key areas including manufacturing efficiency and material longevity. In November 2011 DuPont signed an agreement to allow panel manufacturers such as Samsung to adopt their solution coating process commercially which is a very important step indeed. Scientists in Michigan have also been looking at increasing the lifetime of the blue OLED substrate my taking a different approach. According to Kieffer (the lead researcher), by re-configuring the molecular structure itself it should be possible to significantly extend the useful lifetime of blue substrates – effectively ‘doubling’ their efficiency. These are just examples of important research which could one day overcome the hurdles placed before the commercially viable monitor.
During various trade shows Sony and Panasonic unveiled some prototype large OLED displays with 4K (4096 x 2160) resolutions. These use a technology called ‘Super Top Emission’ which incorporates an RGB pixel design and colour filters. The company claims this enhances colour purity and overall efficiency. However; they currently favour the use of LG Display’s panels, described below. Sony is also pushing out a number of professional monitors using this technology. Samsung hoped to become a dominant force when it came to such technologies, with a number of models shown off at various events and now released into the market. It hasn’t all been plain sailing, however. They have been suffering from a number of issues such as yield and production prices with their ‘Super Top Emission’ technology and had scrapped plans to build a new manufacturing plant for large OLED displays. For TVs and small panels released so far, Samsung has favoured ‘conventional’ RGB OLED design (dubbed ‘Super-OLED’) with direct colour light emission from its organic subpixels. It is worth noting that they have manufactured 13″-14″ OLED panels that have been used in a number of notebooks and tablets designed to run Windows (including a Dell Alienware model). Companies such as Samsung have also put in a lot of research and development effort into RGB OLED applied using an inkjet printing method. They see this application process as particularly useful in the production of monitor panels, as covered in this piece (requires translation from Korean) published December 2018 in ET News.
Samsung curved OLED TV
The other good news for the consumer is that LG Display have recently massively increased their investment in such technology and are really ramping up their production capacity. RWBG (sometimes inaccurately referred to as WRGB) OLED is LG’s current preferred method. As far as models for consumer use LG have a number of large displays (TVs or monitors using ‘TV panels’) on the market which use a colour-filtered RWBG design, some of which are also curved. RWBG is essentially an evolution or sub-category of WOLED (White OLED), featuring colour filters over three organic white subpixels (like traditional WOLED designs) with a fourth subpixel that emits ‘naked’ unfiltered white light. This is designed to enhance the luminance efficiency compared to an RGB OLED or traditional WOLED design with the white pixel able to assist in brightening the image or displaying pure white on its own. As with other implementations this system benefits from luminance control on a per-pixel basis, allowing a pretty much infinite contrast ratio to be achieved. The potential colour gamut is certainly restricted when compared to an RGB OLED design. And so is the colour volume, with saturation levels reduced at high brightness due to the dilutive effect of the unfiltered white subpixel. In terms of solid products for the ‘mainstream’, a 30″ OLED monitor was available for a short period – the Dell UP3017Q. This iteration of OLED is popular for larger panels in the TV market, with some manufacturers dipping their toes into using TV-sized OLED panels for monitors as well. With 42″+ offerings available or announced from various manufacturers, such as the ASUS PG42UQ and lower resolution ultrawide alternatives such as the LG 45GR95QE and Corsair Xeneon Flex (45WQHD240). LG plans to expand production to include ‘mid-size’ RWBG OLED panels in the ~27″ – 32″ size range. The first model which features such a panel is the LG 27GR95QE, with models from other manufacturers which share the same panel.
Other exciting developments came from JOLED, a Japanese joint venture between Sony and Panasonic’s OLED display divisions. Their initial pilot panel was a 21.6″ RGB OLED designed primarily for medical purposes and high-end monitors, such as the ASUS PQ22UC. JOLED moved onto mass-produced panels in monitor sizes of up to 32″, using a technology dubbed ‘TRIPRINT’. Such panels have been used in their own ‘OLEDIO’ line and in products such as the LG UltraFine OLED Pro series and ASUS PA32DC. These are 60Hz models focused on colour-critical workloads. Such models fetch a significant premium ($3000+) as the JOLED panels used are specialised high-end parts produced in relatively low volumes – certainly compared to the scale of many LCD panels. Expansion appeared to be going well for the company, with other monitor manufacturers on board and a continuing drive downwards in product cost. As a later update in that thread confirmed, though, they appear to have been unable to secure the funding they need to expand or potentially even continue with their business and have now filed for bankruptcy. AU Optronics is also getting into the inkjet-printed OLED panel game, with plans for 32″ 144Hz ‘4K’ UHD panels.
Quantum Dots – a non-organic alternative
Note: QLED (Quantum-dot Light Emitting Diode) has been coined by Samsung to refer to solutions that use Quantum Dots in place of phosphors for LED backlights, as described in this article. This would more correctly be termed QD LED, QD Film, Quantum Dot Enhancement Film (QDEF) or something more specific related to the exact technology.
Using Quantum Dots (QDs) as a light source rather than to replace the phosphors in LED backlights is an equally exciting technology. This could bring similar advantages to OLED, without the same concerns about material degradation or brightness limitation. Whilst also allowing greater colour gamut coverage to be achieved due to the exceptional purity of light emitted. This is a complete non-organic alternative to OLED – with self-emissive pixels bringing with it similar key advantages to RGB-OLED designs. You can get a broad perspective of the principles behind ‘QLED displays’ on Wikipedia. Quantum Dots are a far-reaching nanotechnology with many useful applications aside from those involving displays. A lot of initial work in this field that would apply to TVs and monitors was borne of a partnership between QD Vision and LG Display. In addition to sharing or building on the advantages of OLED, such as exceptional contrast and colour gamut support, there were a number of other claims initially made by QD Vision. These include; superior energy efficiency (100% better claimed), higher luminance (30-40% greater claimed) and better stability (read: longer lifetime).
Quantum Dots - an alternative
Back in 2011 MIT Technology review reported a ‘significant step’ towards the demonstration of Quantum Dot display technology for practical purposes. They reported that researchers at Samsung had produced a 4-inch ‘full colour’ monitor. This may not seem like much but it was the first screen to combine red, blue and green subpixels – a solution that could potentially be scaled up to much larger devices (such as computer monitors). The article ended with a few words to inject some further reality to the situation as it was back then. It was a technology that lagged behind OLED in terms of efficiency and there were obstacles related to lifetime still needed to be overcome. This is why we have only so far seen Quantum Dots incorporated into a backlight for existing LCD designs instead.
Now, it seems things are moving forwards nicely. As we mentioned earlier, there are serious concerns with respect to organic material lifetime and degradation – even with current improvements in manufacturing processes. These concerns, coupled with unacceptably high production costs, are sufficient for Samsung to have switched their longer term focus away from relying solely on organic materials for red, green and blue light emission. They have also pivoted away from LCD panel production, with their new technology focus being to use a layer of red and green QDs with a blue OLED ‘backlight’ (per-pixel illumination). A sort of hybrid solution sometimes referred to as ‘QD-OLED’, ‘Quantum Dot OLED’, or ‘QD-Display’. This technology retains many advantages of both technologies and is hopefully scalable for monitor-sized panels. The video below, courtesy of Nanosys and Samsung Display, takes a look at QD-OLED. It covers areas such as the makeup of QD-OLED and their subpixels – with multiple blue OLED layers excited by red and green QDs (via phospholuminescenece) – plus lifetime expectations and performance characteristics.
Nanosys, who have been tremendously successful at integrating Quantum Dots into existing LCD displays, are working towards QDEL (Quantum Dot Electroluminescent) technology; now referred to as ‘NanoLED’ to make it more distinct from the likes of Samsung’s ‘QLED’. This is the ‘pure’ QD solution described above which uses red, green and blue Quantum Dots in a self-emissive display. An early prototype was demonstrated at CES 2023. We have high hopes for this technology and will continue to bring you news on further advancements in this exciting field of monitor technology as soon as we can
Donations are also greatly appreciated.
We can usually easily satisfy our esteemed customers with our very good quality, very good price tag and excellent support as we are more professional, work harder and do it for OLED display module in a cost effective manner
