About the OLED LCD display technology

About the OLED LCD display technology

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An organic light emitting diode (OLED), also light emitting polymer (LEP) and organic electro luminescence (OEL), is a light-emitting diode (LED) whose emissive electroluminescent layer is composed of a film of organic compounds. The layer usually contains a polymer substance that allows suitable organic compounds to be deposited. They are deposited in rows and columns onto a flat carrier by a simple “printing” process. The resulting matrix of pixels can emit light of different colors.

Such systems can be used in television screens, computer monitors, small, portable system screens such as cell phones and PDAs, advertising, information and indication. OLEDs can also be used in light sources for general space illumination, and large-area light-emitting elements. OLEDs typically emit less light per area than inorganic solid-state based LEDs which are usually designed for use as point-light sources.

A significant advantage of OLED displays over traditional liquid crystal displays (LCDs) is that OLEDs do not require a backlight to function. Thus, they can display true black color, draw far less power, and can be much thinner and lighter than an LCD panel. OLED displays also naturally achieve much higher contrast ratio than LCD monitors.

Advantages of the OLED technology

The radically different manufacturing process of OLEDs lends itself to many advantages over flat-panel displays made with LCD technology. Since OLEDs can be printed onto any suitable substrate using an inkjet printer or even screen printing technologies, they can theoretically have a significantly lower cost than LCDs or plasma displays. Printing OLEDs onto flexible substrates opens the door to new applications such as roll-up displays and displays embedded in fabrics or clothing.

OLEDs enable a greater range of colors, gamut, brightness, contrast (both dynamic range and static) and viewing angle than LCDs because OLED pixels directly emit light. OLED pixel colors appear correct and unshifted, even as the viewing angle approaches 90 degrees from normal. LCDs use a backlight and cannot show true black, while an off OLED element produces no light and consumes no power. Energy is also wasted in LCDs because they require polarizers that filter out about half of the light emitted by the backlight. Additionally, color filters in most color LCDs filter out two-thirds of the light; technology to separate backlight colors by diffraction has not been widely adopted.

OLEDs also have a faster response time than standard LCD screens. Whereas the fastest LCD displays currently have a 2ms response time, an OLED can have less than 0.01ms response time. But due to limitations of the human eye, people won’t see a big difference with any video response time under 5 ms.

Disadvantages of the OLED technology
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 (five years at 8 hours a day) when used for flat-panel displays, which is lower than the typical lifetime of LCD, LED or PDP technology—each currently rated for about 60,000 hours, depending on manufacturer and model. However, some manufacturers of OLED displays claim to have come up with a way to solve this problem with a new technology to increase the lifespan of OLED displays, pushing their expected life past that of LCD displays.[45] A metal membrane helps deliver light from polymers in the substrate throughout the glass surface more efficiently than current OLEDs. The result is the same picture quality with half the brightness and a doubling of the screen’s expected life.

In 2007, experimental PLEDs were created which can sustain 400 cd/m² of luminance for over 198,000 hours for green OLEDs and 62,000 hours for blue OLEDs.

The intrusion of water into displays can damage or destroy the organic materials. Therefore, improved sealing processes are important for practical manufacturing and may limit the longevity of more flexible displays.

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Source : Wikipedia