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How Does an OLED TV Work?

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Sony-XEL-1-OLED-HDTV.jpgIf you followed the news coming out of CES 2012, you no doubt heard about the 55-inch OLED TVs that LG and Samsung had on display. Unless you've closely followed the development of OLED over the past few years, you might be wondering what all the fuss is about. You might also be wondering how OLED is different from the "LED" TVs you see on store shelves right now. Why the quotation marks? Because the TVs that currently carry the LED tag aren't really LED TVs at all. They are LCD TVs that simply employ a different type of lighting system. The pixels in an LCD TV can't generate their own light and thus require some type of lighting system. Until a few years ago, that lighting system was generally a CCFL (cold-cathode fluorescent lamp) backlight. Nowadays, many LCD TVs use a lighting system that consists of small LEDs (light-emitting diodes), in either a full-array backlight or edge-lit design. LEDs are more energy-efficient, don't contain hazardous materials, and give you the ability to employ localized dimming to improve the TV's black level and contrast. Marketing types never quite figured out the best nomenclature to describe the difference between these two types of LCDs. LCD TV with LED? LED/LCD? LED-based LCD? None of those choices makes for a good PoS display, so some companies just went with LED TV...much to the annoyance of video reviewers everywhere.

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With that clarification out of the way, let's move on to OLED, which stands for Organic Light-Emitting Diode. An OLED consists of a thin film of organic carbon-based compounds sandwiched between two electrodes. When the compound receives an electric current, it emits light. Because an OLED can generate its own light, it does not require the use of a lighting system the way LCD does, and it can produce a true black (no electric current equals no light). Plasma is also self-illuminating, but plasma pixels are generally "primed" and not truly off, so some light is produced. OLED also has a design advantage over plasma in that all of the compounds and circuitry can reside within one very thin, light (even flexible) sheet, versus the thicker, heavier glass structure required for a plasma TV.

The pixel in an OLED TV currently takes one of two forms. Samsung uses RGB OLED: Each pixel contains a red, green, and blue sub-pixel laid directly on the display panel, which eliminates the need for color filters. LG's approach is called White OLED (or WOLED). As LG describes it, "White OLED uses RGB color layers, which are applied to the organic layer and act as color filters for the light being emitted." CNET's Geoff Morrison recently posted a more thorough description of how White OLED works, which you can read here. In addition to red, green, and blue color filters within each pixel, LG adds a clear filter that allows white light to pass through, which is designed to improve brightness and efficiency. Both types of OLED can provide an expanded color gamut, wide viewing angles, a very fast response time, an incredibly thin and light form, high energy efficiency, and potentially infinite contrast (as I mentioned above, OLED can produce a true black combined with great light output, for an amazing level of contrast). LG embraced the WOLED approach because the company claims that it's more efficient to manufacture and easier to create various screen sizes without sacrificing picture quality. LG says that RGB OLED is a more complex arrangement that's more expensive and harder to scale to different screen sizes, and they believe that WOLED "offers more natural color reproduction and better off-axis viewing than the RGB type." (We asked Samsung for comments on its RGB OLED approach but did not get a response.)

OLED is currently used in mobile devices that have smaller screens (such as phones and gaming devices), but its jump to the TV market has been slow, to say the least. Back in 2008, Sony introduced the XEL-1, an 11-inch OLED monitor that cost $2,500. We thought that might open the gates, but it didn't. (Sony has since abandoned its OLED plans and instead showed off a Crystal LED prototype at CES.) The primary stumbling blocks have been that OLED is expensive to produce at large screen sizes and the organic compounds don't age evenly. The blue compound, in particular, has a shorter life span than the red and green compounds. At this point, the manufacturers are not giving estimates on an OLED TV's longevity; LG's only response was that they believe it will "perform quite well vis-à-vis other displays."

OLED certainly has the potential to be a game-changer in the TV business. Of course, at this stage, potential is the key word. We won't know the full extent of its performance capabilities until we can get our hands on these large-screen TVs and test them for ourselves. The LG 55EM9600 will most likely be the first OLED TV to market later in the year. LG has not officially announced a price; however, back in early January, DisplaySearch estimated that its price would be around $8,000.


More resources: HowStuffWorks.com, OLED-Info.com, CNET

Additional Resources
• Find more original commentary like this in our Feature News Stories section.
• Read more LED HDTV news from HomeTheaterReview.com.
• Explore reviews in our LED HDTV Review section.

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