For years manufacturers have tantalized consumers with the promise of organic light-emitting diode (OLED) televisions capable of delivering more brilliant colors (including deeper blacks), and greater levels of contrast and brightness than any other television screen—all with rapid video response rate. OLEDs are already in regular use to provide crystal-clear screens for smart phones, car stereos and digital cameras.

Still, if you went shopping this year for an affordable OLED TV with a display big enough for any room other than a closet, you were sorely disappointed because it doesn't exist. The situation is likely to change in 2012 when LG and rival Samsung unveil competing 140-centimeter OLED displays—the largest ever made—at next month's Consumer Electronics Show (CES) in Las Vegas.

What's the big deal? OLEDs are made by placing thin films of carbon-based materials between two conductors and applying an electrical current to generate a bright light. This makes OLEDs thinner, lighter and more flexible than the crystalline layers in an LED or LCD. Whereas LCDs work by selectively blocking areas of light generated at the back of the display, OLEDs generate light themselves (each pixel is a small light-emitting diode). Because they don't need to be backlit they consume less power than LCDs.

In terms of pure entertainment value, a 140-centimeter OLED TV is more than three and a half times the size of any other OLED on the market. (LG sells a 38-centimeter display in Europe and its native South Korea for as much as $2,600.) Sony (pdf) and others are developing OLED TVs, but nothing as big as what LG and Samsung are promising. Both models are expected to be available by mid 2012, in time for the Summer Olympics in London.

LG claims that its new OLED TV, which is only five millimeters thick, will have a contrast ratio of more than 100,000:1. The contrast ratio is the proportion of the luminance of a display's brightest white to that of its darkest black. The higher the ratio the better the viewing experience. To put this in perspective, under optimal (dark) conditions, a movie theater screen achieves a contrast ratio of 500:1. Living rooms are rarely dark enough for a traditional TV to pull off even that level of contrast.

However, complexity and cost of materials have helped keep OLED screen sizes small and prices high. Because an OLED TV has a transistor backplane that controls the brightness of each pixel, millions of these transistors are required to create images on the screen. An OLED is more energy efficient and produces a clearer picture than an LCD screen because it deposits red, green and blue pixels where each of these transistors is positioned. LG claims to have simplified the design of its 140-centimeter display in part by using white OLEDs with color filters. The use of these filters—as well as cheaper, more efficient materials to make the transistors—is helping the company to scale up the size of its OLED displays without a commensurate rise in cost. Neither LG nor Samsung have announced pricing for their new OLED displays.

Image of Sony's 28-centimeter XEL-1 OLED TV (circa 2007) courtesy of Steve Liao, via Flickr