How works the OLED technology?

OLED Organic light emitting diodes displays are considered as the screens of the future.

What is OLED?

OLED stands for Organic Light Emitting Diode. The “organic” in OLED refers to organic material. Carbon is the basis of all organic matter. Examples of carbon-based substances include sugar, wood and the majority of plastics. The “LED” stands for “Light Emitting Diode” and describes the process of converting electric energy into light. There are two types of OLEDs small molecule OLED and polymer OLED. Sony uses the small molecule type because it has a longer lifespan.

What’s so great about OLED?

Blazing fast response times, wide viewing angles, exceptional color reproduction, outstanding Contrast levels, and high Brightness. The nature of its technology lends itself to extremely thin and lightweight designs along with the ability to use it in a variety of different applications. OLED is the holy grail of TV Display technologies!

How does OLED work?

A Layer of organic material is sandwiched between two conductors (an anode and a cathode), which in turn are sandwiched between a glass top plate (seal) and a glass bottom plate (substrate). When electric Current is applied to the two conductors, a bright, electro-luminescent light is produced directly from the organic material.

How is color created?

OLED has more control over color expression because it only expresses pure colors when an electric Current stimulates the relevant Pixels. The OLED primary color matrix is arranged in red, green, and blue Pixels, which are mounted directly to a printed circuit board. Each individual OLED element is housed in a special “micro-cavity” structure designed to greatly reduce ambient light interference that also works to improve overall color Contrast.
The thickness of the organic Layer is adjusted to produce the strongest light for each of the colors ” red, green and blue – used to render the color picture. The three colors are further refined by a color filter, which purifies each color without the need for a polarizer, rendering outstanding color purity.
Organic light emitting diodes have been receiving a lot of attention over the world as a new type of display technology. OLEDs have many advantages over conventional display technologies. First, the fabrication process is easy, and devices are thinner and lighter than those fabricated by cathode ray tube (CRT) display technology.
Second, there are also some advantages over liquid crystal (LCD) displays: OLEDS can be viewed from different angles and don’t need a backlight. Finally, the drive voltage and power consumption are low. The first commercial OLED display was introduced by Pioneer Electronics as the front panel of a car stereo in 1997.

Video from Discovery Channel and Kodak

To enhance the colour or brightness, manufacturers can add complex chains of molecules (polymers) to the carbon-based layers.

Unlike LCDs, which require backlighting, OLED displays are “emissive” devices, meaning they emit light rather than modulate transmitted or reflected light.

Thin organic layers serve these displays as a source of light, which offers significant advantages in relation to conventional technologies:

• brighter and more brilliant picture
• unlimited viewing angle
• low power consumption
• economic production
• fast “response time”

The prerequisites for a breakthrough of this technology in the market, which is estimated in 2010 to be worth over USD 2 billion, are the optimization of certain critical performance data such as lifetime and efficiency. This requires innovations in materials meaning that chemistry will decide about the future and the success of the OLED technology. OLEDs – Organic Light-Emitting Diodes are the light of the future
Video wallpaper – just a millimeter thick – could transform your living room wall into a flat screen and electronic film as thin as a sheet of paper could serve as your screen for the internet, the news, images or games. In future, all of this will be possible thanks to organic light-emitting diodes, so-called OLEDs. In this episode you will learn more about this revolution in lighting technology:

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Why are the OLED-Display technology even better than the LCD or plasma technology?
Low power consumption is the reasen why OLED is a better choice for portable devices. It also makes OLEDs, and a candidate to be the white-light “bulb” of the future Greater brightness.
Light sources based on organic electroluminiscent materials offer the potential to make a high light intensity possible at a low energy consumption on mechanically flexible substrates.” said project head Prof. Dr. Karl Leo (IAPP) about the high expectations.

- The Flat screen are brighter, and have a fuller viewing angle. Better durability – OLED-Displays can operate in a temperature range Lighter weight – the screen can be made very thin, and can be ‘printed’ on flexible surfaces.
Many electronic appliances are at the threshold of a revolution that began with the discovery of polymeric conductors in the 1970s. Polymeric materials, which have historically been classified exclusively as electrical insulators, are now finding varied applications as both conductors and semiconductors. Expensive ceramic semiconductors that are brittle and difficult to pattern have historically been the driving force of the digital age for the last fifty years. But now a combination of properties exist today in polymers that are making many previously impossible appliances a reality.
Within a very short time organic conductors have been developed with the conductivity of metals such as copper, while organic electronics has evolved photoelectric cells, diodes, light emitting diodes, lasers and transistors. The result is that a class of plastic materials referred to as conjugated polymers are fast displacing traditional materials such as natural polymers (e.g. wood), metals, ceramics and glass in many applications owing to the combination of their physical/mechanical properties (light weight combined with physical strength) and ease of processibility (the ability to mould the shape of plastic materials or extrude into sheet and rod through a die).
What this means is that OLEDs can be deployed in a wide range of electronic devices and can be used extensively throughout any given device. Active components of displays can be polymers, substrates can be polymers, logical electronics can be polymers, and so on. In the years ahead OLEDs will see applications in personal computers, cell phones, televisions, general wide area lighting, signs, billboards, communications and any of a number of information appliances.
The basic OLED cell structure consists of a stack of thin organic layers sandwiched between a transparent anode and a metallic cathode. The organic layers comprise a hole-injection layer, a hole-transport layer, an emissive layer and an electron-transport layer. When an appropriate voltage (typically a few volts) is applied to the cell, the injected positive and negative charges recombine in the emissive layer to produce light (electroluminescence). The structure of the organic layers and the choice of anode and cathode are designed to maximise the recombination process in the emissive layer, thus maximising the light output from the OLED device. Both the electroluminescent efficiency and control of colour output can be significantly enhanced by “doping” the emissive layer with a small amount of highly fluorescent molecules.
AM OLED = Active Matrix OLED device