OLED, or Organic Light Emitting Diodes, are an offshoot of existing conventional LED technology. LEDs are semiconducting light sources that function through electroluminescence—that is, they produce photons (aka light) by plopping electrons into little electron holes within the device's emissive layer. Basically, electricity goes in and light comes out thanks to a semiconductuctive material, rather than a white-hot metal filament like an old-school lightbulb.
OLED technology, first successfully implemented in 1987 by Kodak researchers Ching W. Tang and Steven Van Slyke, takes this same idea as LED, but flattens it. Rather than an array of individual LED bulbs, OLED uses a series of thin, light emitting films. This allows the OLED array to produce brighter light while using less energy than existing LCD/LED technologies. And since these light-emitting films are composed of hydrocarbon chains, rather than semiconductors laden with heavy metals like gallium arsenide phosphide, they get that "O" for "organic" in their name.
An OLED panel is typically composed of four primary layers: The substrate, which acts as the structural framework; the anode, which draws electrons; the cathode, which provides electrons; and the organic layer between. That organic layer is further divided into a conducting layer—which provides the "electron holes" that the electrons flowing through layer can snap into, shedding energy in the process—and an emissive layer where the light is actually produced. And if you want to start messing with producing actual color, it's just a matter of adding red-, green-, and blue-tinted plastic layers to the substrate.
There are additional flavors of OLEDs that are better for different kinds of devices. When a device only needs to display a static pattern with relatively slow refreshes—like the LCD readout of a calculator or e-ink displays of the Kindle Paperwhite—you can use something called a passive matrix OLED (or a PMOLED). These work by turning on voltage to specific areas of the film and leaving them on until the device refreshes its instructions.
Then there's active matrix OLEDs, like the AMOLEDs you might find in a smart phone. These are for high-definition applications that demand fast refresh rates, such as smartphone screens or HD televisions. AMOLED displays require a thin film transistor back-plane to actually drive each of the individual pixels, but this layer is just as flexible as the others, allowing for the development of rollable, foldable, transparent display panel prototypes.
Why's it so great?
The LEDs in today's LED televisions are actually used only to provide a white back light, which then shines through a rapidly-refreshing LCD shutter array which tints the emanating light. OLEDs, on the other hand, operate as both light source and color array simultaneously. This may not sound like a big difference, but does offer a wide range of benefits including:
- Lower power consumption - An OLED display doesn't need any of the electronics and circuitry used to drive the LED back light and LCD shutter from a LED display, which makes OLEDs more efficient. LED screens produce black simply by fully closing the pixel shutter—the back light is still shining (it never actually turns off) but the light itself is being blocked. An OLED instead turns the pixel off entirely to produce the color black, saving energy in the process.
- Better picture quality - Since OLEDs incorporate their own color filters, they can produce deeper blacks and a wider gamut array. The lack of a permanently-on backlight promotes higher contrast ratios (the difference between the brightest and darkest pixels on the screen). And thanks to the lack of a shutter array, OLED displays can have refresh rates that are an order magnitude faster than those of LCD/LED sets. We're talking a boost from 480 Hz to 100,000 Hz—theoretically, at least. On top of that, OLEDs offer an impressively wide viewing angle—nearing 90 degrees off center for many panels—without the color and clarity losses seen in traditional LEDs.
- Better durability and lighter weight - Ditching the back light and shutter arrays also means manufacturers can replace the heavier, shatter-prone glass substrates often used in LED displays with lighter, stronger plastic substrates. And with the advent of injet-based printable OLEDs, these light producing compounds can be applied to more exotic and malleable surfaces. Additionally, the OLED films themselves are quite durable and can withstand a wider operating temperature range than regular LEDs without failing.
- The price is only going down from here - The ability to simply print out OLEDs as you would a term paper or silk-screened t-shirt holds incredible technological potential. It's also ludicrously expensive at present—look to spend about triple for an OLED set than a conventional LCD/LED these days—but once roll-to-roll production capabilities are scaled up sufficiently, the cost of spitting out an OLED panel should drop below what we're paying to make current generation LEDs.
OLED technology isn't without its drawbacks and shortcomings. The biggest issue facing OLED right now is the fact that the material used to produce blue light degrades at a much faster rate than the other hues, which eventually throws off the color balance and reduces the overall brightness of the display.
This forces manufacturers to compensate by, say, drastically increasing the size of the blue sub-pixel to as much as double the green and red, or requiring the consumer to continually fiddle with the calibration. Luckily, a great deal of research has been made into improving the efficiency and lifespan of blue OLED, culminating in a recent breakthrough that has brought the hue up to par with its other subpixels.
To be clear, the composition of the display panel—whether it's a CRT, plasma, LED, or OLED—has very little to do with the resolution of the screen. The terms, HD, 4K, and UltraHD all refer to the number of pixels the manufacturer can pack into a panel, not what those pixels are made of or how they work. This is why you can find sets like Sony's flagship 4K XBR-65X950B using LCD/LED panels and 1080p sets like the LG EC 9300 sporting OLED displays.
If you're currently in the market for a TV that is both future-proof and offers a superior image, you're going to be paying through the nose for something like LG's obscenely expensive 4K OLEDs. Conversely, you could split the difference, depending on how soon you think you'll be buying your next set, and either opt for a 4K LCD/LED or a 1080p OLED. Just don't waste your cash on a 1080p LED; that tech is already in the past, replaced by a bright and glorious future. [OLED Info - Wiki 1, 2 - How Stuff Works - Explain that Stuff - PC Mag - Cornell University]
source: gizmodo.com by Andrew Tarantola