Electroluminescence

Electroluminescence (EL), also called Destriau effect, a form of luminescence in which a solid is excited by applying an electric field or an electric voltage to electromagnetic radiation, for example in the form of light to emit.

History

The effect was discovered in 1936 by the scientist Georges Destriau, in 1936 in the laboratory of nuclear physicist Marie Curie experimented on a metal alloy to test their conductivity. The zinc sulphide used by him was inadvertently contaminated with copper and showed a light emission than he put strong electric fields to the alloy.

The technical use was not possible because of the time very short lifetime of the experimental setups. This resulted mostly from inadequate partitioning of the light-emitting layers to oxygen and water. Destriau the material developed further to a production-ready product, the so-called electroluminescent film, which was first used in the military in the cockpit and the wing lights. Because of advances in material science and better encapsulations Today, for example, as a backlight for an LCD display possible use.

1962, light emitting diode ( LED) has been invented, a semiconductor device which emits light when an electric voltage. The phenomenon is based is also referred to in this case as electroluminescence, although the physical mechanism of the effect discovered by Destriau different (see " mechanisms and components "). LEDs have experienced a large spread as a display and lighting elements ever since. With the development of organic light emitting diodes ( OLED) since 1987, which are also counted as electroluminescent devices, the application of LEDs has expanded again.

Mechanisms

Of the possible physical mechanisms to encourage a solid body by applying an electric field to emit light, the following are two of technical importance.

Alternating field excitation ( Destriau effect)

The radiators, for example, an electroluminescent film is constructed as a capacitor. The electroluminescent material, typically doped with metals, zinc sulfide (for example, ZnS: Mn) is isolated from the electrodes. By applying a strong alternating electric field, electrons are accelerated in the electroluminescent layer. Shocks to the impurities produced by the doping put electrons into excited states, which fall under the emission of light in the ground state. The required voltage for excitation is 10 kV / cm. Thin layers meet several 100 V with a frequency of 200 to 4000 Hz

DC voltage excitation (p -n junction )

Doped semiconductors generate light in the p-n junction of a light emitting diode at a low voltage. Here, various semiconductor materials are used, for example, AlGaAs, GaAsP, GaP and GaN whose bandgap More specifically, the color of the emitted light.

Organic light emitting diodes work on a similar principle, but they are constructed as Schottky diodes, ie have two electrodes with different work functions, in contrast to inorganic LEDs. The emitting materials, organic semiconductors such as Alq3 are used.

Other suggestions

If the definition of electroluminescence not limited to, solid-state, so include in the strict sense, gas discharge lamps have contributed, however, the term in this context is not common.

Sometimes the cathodoluminescence and Radioluminescence are referred to as electroluminescence.

Components

• Electroluminescent film; other names: light tile, electroluminescent tube, electroluminescent wire