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What is OLED and what can it do for your TV?

For the last several years the TVs with the best picture quality have used OLED, or Organic Light Emitting Diodes. Curious what makes them different from other TVs? You've come to the right place.

Andrew Hoyle/CNET

OLED televisions offer exceptional images at exceptionally high prices.

What makes them different from the LCD TVs in most homes? How does their different nature make for better-looking images? Why are they so expensive? Answers to these questions and a bunch more you probably haven't thought of, below.

Though we've covered this before, we figured we'd take a look at where we're at now and in the near future.

Organic contrast

OLED stands for Organic Light Emitting Diode. Each pixel in an OLED display is made of a material that glows when you jab it with electricity. Kind of like the heating elements in a toaster, but with less heat and better resolution. This effect is called electroluminescence, which is one of those delightful words that is big, but actually makes sense: "electro" for electricity, "lumin" for light and "escence" for, well, basically "essence."

What's the "organic" part? The specific electroluminescent materials used in OLED displays are organic compounds, which means they contain carbon plus some other ingredients. Each color requires a different organic compound (though these aren't necessarily the colors you see on the TV, but more on that later).

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The effect is that each tiny OLED pixel in the screen creates light depending on how much electric current you send it. Lots of current, lots of light. No current, no light. And that's one key to OLED's excellent picture quality.

OLED TV marketing often claims "infinite" contrast ratios, and while that might sound like typical hyperbole, it's one of the extremely rare instances where such claims are actually true. Since OLED can produce a perfect black, emitting no light whatsoever, its contrast ratio (expressed as the brightest white divided by the darkest black) is technically infinite. And contrast ratio is arguably the most important aspect of picture quality.

OLED vs. LCD

OLED is the only technology capable of absolute blacks and extremely bright whites on a per-pixel basis. LCD definitely can't do that, and even the vaunted, beloved, dearly departed plasma couldn't do absolute blacks.

Why can't LCD do that? The liquid crystal that makes an LCD an LCD only blocks the light created by its backlight. Basically like putting sunglasses in front of a candle. Even the best LCDs can't completely block all the light, so in order to get those inky movie-theater-like blacks, you have to turn the backlight down (the "candle").

In the most LCDs, the entire backlight works as one, dimming the entire screen (if that). Local dimming LED LCDs are far better, but still only dim and brighten relatively large sections of the screen independently. OLED TVs' "dimming," on the other hand, operates on a per-pixel basis. So while the best local dimming LED LCDs may have 6 or 12 or 64 or 300 dimming zones on the screen, a 4K OLED TV has more than 8 million.

OLED doesn't have the extreme light output of the best current-generation LCD TVs, but it's still very bright, has better blacks for a better contrast ratio, and can dim and brighten the screen on a per-pixel basis. So TV shows and movies -- from standard-def to high-def to 4K with High Dynamic Range -- really pop.

Yellow plus blue makes green (and red and cyan and magenta)

Currently, all OLED TVs are made by LG, and how they've made them is rather unusual. All TVs, to create the images you watch, use red, green, and blue mixed together to create all the colors of the rainbow (well, not quite all colors, but most). To create the colored light, LCDs use RGB color filters, while plasmas used RGB phosphors and Samsung's short-lived OLED TV (and all their OLED-screened phones) use red, green and blue OLED elements.

LG's OLED only use two colors: a sandwich of blue and yellow OLED. Then, using color filters, the yellow and blue light is filtered to create red, green and blue. To add a bit more brightness, there's also a clear "white" element, too. It's a lot easier if I show you:

lg-oled-blue-yellow.jpg

The steps to create an image with LG's OLED.

A yellow OLED material creates yellow (i.e. red and green) light. When combined with blue (1), this creates "white" light (2). Using color filters (3) the desired sub-pixel color (including clear/white) is created (4).

Geoffrey Morrison

Though this seems odd and convoluted, it obviously works since LG is the only company that has successfully marketed large-screen OLED TVs in any numbers. This is because it's more cost-effective to make ("more" being the key word there).

The apparent downsides, such as light output and color accuracy, don't seem to be issues. Sure, they're not as bright as the brightest LCDs, but they are still very bright, and the 2016 models have some of the widest P3 color gamut coverages CNET has measured.

Most of the information above is based on what LG told me when I wrote the last version of this article in 2014. When asked to verify this was still how LG OLEDs worked, and if anything had changed, an LG spokesperson replied, "We improved the efficiency and color gamut by changing materials and structure, but we cannot comment on details as they are confidential."

I take that to mean that they really haven't changed anything major about how they manufacture OLED...they've just grown more wary about discussing it.

Lifespan

The most common question I get about OLED TVs is about how long they'll last. The blue OLED material was always shorter-lived than other "flavors" of OLED. But wait! I hear you exclaim. Wouldn't that mean the LG's whole TV will die out at the faster blue rate, since every pixel incorporates blue? Apparently pairing the blue OLED with yellow, as LG did, provides longevity benefits.

According to LG's spokesman: "We have secured a lifespan for OLED TV's of more than 50,000 hours, which is generally longer than conventional TVs." So if you watch six hours of TV a day, that's over 22 years of use.

At least, that's how long they expect the panel to last. On most modern TVs of any technology, it's the power supply that dies long before the panel. Not to mention that a TV bought today probably won't be able to be connected to anything in 22 years (just like TVs circa 1994 are obsolete today). But that's for a different article.

The future

Like any technology, we'll see larger, cheaper and better OLEDs from LG, at least in the short term. However, it should worry every fan of great picture quality that only one company is making OLED TVs. If nothing else, competition from another maker should drive down prices.

With Samsung seemingly conceding the OLED TV space to LG, Sony and Panasonic's attempts being MIA or restricted to Europe like Philips, and no Chinese manufacturer making serious inroads, it doesn't look like anyone else will compete against LG in the mass market anytime soon. On the other hand, LG keeps expanding the number of models, sizes and price points, which is a good sign.

nanosys-qled-hero-amanda-carpenter-and-oleg-grachev.jpg

Two vials of photoluminescent quantum dots next to a prototype blue photoelectroliminescent QD.

Nanosys - Amanda Carpenter and Oleg Grachev

One of the most promising current LCD technologies is quantum dots. These microscopic particles glow a certain color when you give them energy. Many new TVs have the photoluminescent version, with dots that glow a specific color when hit with light (usually the light from an LED backlight). These help LED LCDs achieve the deeper colors required of the Wide Color Gamut aspect of High Dynamic Range (HDR).

Down the road a little farther is the electroluminescent version of this technology. No LED backlight at all; just pixels made of quantum dots. These direct-view quantum dot displays, "QLED" if you will, should offer all the benefits of OLED at even cheaper prices. This is something Samsung is looking into, since they couldn't get OLED to work in large screen sizes.

Perhaps most interesting, these aren't mutually exclusive technologies. Quantum dots (the photoluminescent version) don't really care what kind of light you give them. So you could have an OLED material creating one color of light, with quantum dots creating the other colors (instead of color filters). Maybe that would be QOLED ("Quoh-lead")? Q-DOLED ("Que-doh-lead")?

Either way, we shall see.

Bottom line

OLED displays are expensive, but their drop in price from just a few years ago is dramatic. That has leveled off somewhat, but in return they've gotten even better, with higher brightness and wider color gamut.

We've reviewed several OLED models over the years, and they consistently make fantastic-looking images. How fantastic? Here's what David Katzmaier thought of this year's B6: "LG's high-end 2016 OLED TVs deliver the best picture quality of any TV we've ever reviewed...."

Would we like to see them even cheaper, and made by more than one company? Absolutely. Until then, they sure make some lovely images.


Got a question for Geoff? First, check out all the other articles he's written on topics such as why all HDMI cables are the same, LED LCD vs. OLED, why 4K TVs aren't worth it and more. Still have a question? Tweet at him @TechWriterGeoff then check out his travel photography on Instagram. He also thinks you should check out his sci-fi novel and its sequel.