Televisions

Its simple construction has hopes pinned on OLED technology. While other screens produce the light through complicated use of electron beams or discharges, or with a backlight, every OLED pixel converts power directly into photons of light.

In principle, all you need for this is a circuit to control the flow of power, and a luminous coating - the so-called substrate - superimposed onto any surface. The chemical phenomenon behind the light production is called luminescence or "cold light", since - unlike many other light sources - it is not associated with the generation of heat.

You will know the effect, for example, from "phosphorescent" material, which has a long afterglow in the dark. The alternative "fluorescence" process is more important for screens because the illumination disappears quickly once energy is shut off.

Differences in terms of materials:

OLEDs are a type of light-emitting diode but differ from normal LEDs in terms of the materials used: Instead of crystals, they use carbon-based compounds - "organic" materials colloquially referred to as plastics.

• Small molecules that are composed of purely organometallic compounds, based on aluminum, for example.

• Polymers, a type of long-chain molecule, which emit light in certain compounds and after electrical excitation. This process is sometimes referred to as PLED.

For some time mixed varieties also pop up, in which non-emissive polymers mix with luminescent molecules. Various manufacturing technologies are possible depending on the material (see "The Situation Today").

Besides the luminescent material, a transport layer is required (or in some cases even two layers that transport the electrons) and shields the anode. Some OLEDs also use color filters in addition to the luminescent materials.

Active or Passive Matrix:

A circuit and a semitransparent layer composed of indium tin oxide (also used in LCDs) control the power. It is important to differentiate between simple monochromatic displays, where a passive matrix controls power, and color displays, which use an active matrix circuit (referred to as AM-OLED). Active matrix generally refers to TFT (Thin Film Transistor), as used in LCD, but with a slightly different construction.

The technology emits light toward the anode or the cathode, depending on the construction: Undirected emission would obviously be a hindrance, so the type of construction is important. You can significantly increase the efficiency by using reflective coatings, for example.

Organic LEDs aren't just limited to screens:

They're also interesting for general illumination since they're energy efficient, moreso than many of today's other light sources. They can also illuminate large areas. One application could entail using transparent sheets to turn windows into lamps at night. Already, OLEDs are used for backlighting small LCD screens.

OLED - more environmentally-friendly:

OLED rises as a pioneer of so-called "organic electronics". While silicon-based circuits are etched from a large parent material, so to speak, organic materials can be dosed out precisely so material is only applied where it's actually needed. This is significantly more environmentally-friendly, and of course also cheaper in the long run. The abbreviation "OEL" (Organic Electroluminescence) is also sometimes used for OLED.

OLED Technology Explained