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OLED TV the future of flat screen televisions (Organic Light Emitting Diode)
source: Sony and others

OLED TV's are about to revolutionise the way we watch TV. In fact OLED technology is here now.

Sony OLED TVOLED screens are starting to appear in small hand held devices such as phones, PDA's Netbooks and even watches. Larger screens for desktop computers are also available now.

OLED (Organic Light Emitting Diode) according to wiki is:

An organic light emitting diode (OLED), also organic electro luminescent device (OELD), is a light-emitting diode (LED) whose emissive electroluminescent layer is composed of a film of . This layer of organic semiconductor material is formed between two electrodes, where at least one of the electrodes is transporganic compoundsarent.

OLEDs can also be used in light sources for general space illumination, and large-area light-emitting elements. Due to the younger stage of development, OLEDs typically emit less light per area than inorganic solid-state based LEDs which are usually designed for use as point-light sources.

Currently, flat screen TVs are created using two different technologies: Plasma and Liquid Crystal Display (LCD). The foundation of the plasma TV is over a million tiny glass cells that are charged with a mixture of neon and xenon. Behind these cells are colored phosphors, which are chemical compounds that emit light when energised.
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Each cell has three phosphors; one red, one blue, and one green. When activated by an electrode, the plasma cells emit invisible UV light.

OLED is not unlike the LED or the small lights that flash and blink in modems, tell you you favourite appliance is on, or even tell you the time in your bedside clock. The difference is it's much much smaller and when arrange in an array of red green and blue, can produce a sharp clean and crisp image on screen. Compared to existing TV technology, it's very energy efficient.

LED or Light-Emitting Diode was the first solid state light producing device which emits a bright light when current is passed through it and it is long lasting as it has no filament and uses very little power. Sony then used LEDs in screens for large stadiums but couldn’t translate that into a home use product that was practical due to the large power consumption and size.

LCD then came to the forefront for home use and office products as it used small amounts of electricity but it doesn’t emit light, so it needed a light source behind it to see the images.

OLED meets the requirements of having the pixels which an LCD screen has, but also produces a bright light. It has the colours red, blue and green which are produced when an electric current passes through a series of thin organic films between two electrodes. Each pixel can be controlled individually by using semiconductor technology which then produces the picture on the screen. The process is called electrophosphorescence which is also seen in nature in the form of fireflies. OLED panels are extremely thin (like a piece of paper) and are flexible with a wide viewing angle of 170 degrees. As they produce their own light they do not need backlighting like an LCD and therefore need very little power to operate.

Pros and Cons

Size and Weight
OLED screens are incredibly thin and flexible. It's possible to bend, even roll up the membrane that forms an OLED TV. OLED screens are typically the width of a couple of credit cards. The Sony XEL1 picture above is only 3.3mm thick. The associated electronics is in the base unit below the screen. The screen size of the Sony unit above is only 11" which is very small compared to LCD and Plasma, but that will change very soon.

OLED TV is brighter than any of the back lit passive technology used in HDTV

Contrast Ratio
OLED screen contrats ratio is typically and amazingly 1,000,000:1 Contrast ratio is the measurement of the brightest white against the blackest black that the TV can create. The higher the contrast ratio, the easier it is to discern details on the screen. Current plasmas measure contrast ratios of up to 3000:1. However, independent reviewers believe that measured in real world viewing situations, contrast ratios for plasma TVs drop to approximately 200:1. Conversely, LCD TV contrast ratios range from 350-450:1 when measured using the same realistic standards.

Additionally, as the OLED material used to produce blue light degrades significantly more rapidly than the materials that produce other colors, blue light output will decrease relative to the other colors of light. This differential color output change will change the color balance of the display and is much more noticeable than a decrease in overall luminance. This can be partially avoided by adjusting colour balance but this may require advanced control circuits and interaction with the user, which is unacceptable for some uses.

Screen Size
Right now, the plasma market offers TVs as big as 60 inches, and no plasma TV is available smaller than 32 inches. LCD screen sizes range from 13 inches to 46 inches, and because of manufacturing innovations, larger models are becoming available every year. Look for LCDs to catch up in this area soon.

Viewing Angle
Historically, plasma TVs have had a larger viewing angle, at about 160 degrees, when measured against older LCD TVs. However, the newer model LCD TVs have viewing angles up to 175 degrees. OLEDs can enable a greater artificial contrast ratio (both dynamic range and static, measured in purely dark conditions) and viewing angle compared to LCDs because OLED pixels directly emit light. OLED pixel colours appear correct and unshifted, even as the viewing angle approaches 90 degrees from normal. LCDs filter the light emitted from a backlight, allowing a small fraction of light through so they cannot show true black, while an inactive OLED element produces no light and consumes no power.

Typical plasma TVs have a life span of 20,000 to 30,000 hours, which equates to at about 20 years of usage if you have the set on for 4 hours a day. The lifespan of an LCD TV is typically 50,000 to 60,000 hours, or about 40 years running 4 hours daily. The biggest technical problem for OLEDs is the limited lifetime of the organic materials. In particular, blue OLEDs historically have had a lifetime of around 14,000 hours to half original brightness (five years at 8 hours a day) when used for flat-panel displays, which is lower than the typical lifetime of LCD, LED or Plasma technology—each currently rated for about 60,000 hours to half brightness, depending on manufacturer and model. However, some manufacturers displays aim to increase the lifespan of OLED displays, pushing their expected life past that of LCD displays by improving light outcoupling, thus achieving the same brightness at a lower drive current.

Response Time
OLED TVs reacts faster to changes in signals than plasma or LCD TVs which make them ideal for full motion video

Power Conservation
While an OLED will consume around 40% of the power of an LCD displaying an image which is primarily black, for the majority of images, it will consume 60-80% of the power of an LCD - however it can use over three times as much power to display an image with a white background such as a document or website. This can lead to disappointing real-world battery life in mobile devices. Due to not needing backlights OLED TV uses less power than plasma and LCD TVs

OLED is the new kid on the block. It promises much, but is still in its infancy. Our advice: sit tight for a while.

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