NationMaster - Encyclopedia: Electroluminescence

Electroluminescence (EL) is an optical phenomenon and electrical phenomenon where a material emits light in response to an electric current passed through it, or to a strong electric field. This is distinct to light emission resulting from heat (incandescence) or from the action of chemicals (chemoluminescence). Image File history File links EL_unlit-lit_animation. ... Image File history File links EL_unlit-lit_animation. ... Reflective twisted nematic liquid crystal display. ... Backlights are lights that are attached to LCD displays so that they can be seen at night. ... An optical phenomenon is any observable event which results from the interaction of light and matter. ... Electrical phenomena are commonplace and unusual events that can be observed which illuminate the principles of the physics of electricity and are explained by them. ... Electric current is the flow of electric charge. ... In physics, an electric field or E-field is an effect produced by an electric charge (or a time-varying magnetic field) that exerts a force on charged objects in the field. ... This page is a list of sources of light. ... Molten glassy material glows orange with incandescence in a vitrification experiment. ... Lightsticks Chemoluminescence (sometimes chemiluminescence) is the emission of light (luminescence) as the result of a chemical reaction. ...

Mechanism

Electroluminescence is the result of radiative recombination of electrons and holes in a material (usually a semiconductor). The excited electrons release their energy as photons - light. Prior to recombination, electrons and holes are separated either as a result of doping of the material to form a p-n junction (in semiconductor electroluminescent devices such as LEDs), or through excitation by impact of high-energy electrons accelerated by a strong electric field (as with the phosphors in electroluminescent displays). Radiative recombination is a term used for an electron falling from a high energy orbital into a lower one via the simultaneous emission of a photon. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... In solid state physics, an electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... In physics, the photon (from Greek Ï†Ï‰Ï‚, phÅs, meaning light) is the quantum of the electromagnetic field; for instance, light. ... In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ... A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ... External links LEd Category: TeX ... A phosphor is a substance that can exhibit the phenomenon of fluorescence (glowing during absorption of radiation of another kind) or phosphorescence (sustained glowing without further stimulus). ...

Examples of electroluminescent materials

Zinc sulfide is a chemical compound with the formula ZnS. Zinc sulfide is a white to yellow colored powder or crystal. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ... General Name, Symbol, Number silver, Ag, 47 Chemical series transition metals Group, Period, Block 11, 5, d Appearance lustrous white metal Atomic mass 107. ... For other uses, see Diamond (disambiguation). ... For other uses, see Diamond (disambiguation). ... General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Atomic mass 10. ... A dopant is an impurity element added to a semiconductor lattice in quite low concentrations in order to alter the optical/electrical properties of the semiconductor. ...

Practical implementations

Phosphor-based electroluminescent panels are frequently used as backlights to liquid crystal displays. They readily provide a gentle, even illumination to the entire display while consuming relatively little electric power. This makes them convenient for battery-operated devices such as pagers, wristwatches, and computer-controlled thermostats and their gentle green-cyan glow is a common sight in the technological world. They do, however, require relatively high voltage. For battery-operated devices, this voltage must be generated by a converter circuit within the device; this converter often makes an audible whine or siren sound while the backlight is activated. For line-voltage operated devices, it may be supplied directly from the power line. Electroluminescent nightlights operate in this fashion. Image File history File links NightLight. ... Image File history File links NightLight. ... A nightlight is a small, usually electrical, light source placed for comfort or convenience in indoor dark areas or areas that become dark at certain times. ... Backlights are lights that are attached to LCD displays so that they can be seen at night. ... Reflective twisted nematic liquid crystal display. ... It has been suggested that this article or section be merged with Paging (telecommunications). ... This page is about timekeeping devices. ... Bi-metallic thermostat for buildings A thermostat is a device for maintaining the temperature of a system within a range by controlling, either directly or indirectly, the flow of heat energy into or out of the system. ... Green is any of a number of similar colors. ... Cyan is a pure spectral color, but the same hue can also be generated by mixing equal amounts of green and blue light. ... A nightlight is a small, usually electrical, light source placed for comfort or convenience in indoor dark areas or areas that become dark at certain times. ...

In either case, the EL material must be enclosed between two electrodes and at least one electrode must be transparent to allow the escape of the produced light. Glass coated with indium oxide or tin oxide is commonly used as the front (transparent) electrode while the back electrode is or is coated with reflective metal. General Name, Symbol, Number indium, In, 49 Chemical series poor metals Group, Period, Block 13, 5, p Appearance silvery lustrous gray Atomic mass 114. ... General Name, Symbol, Number tin, Sn, 50 Chemical series poor metals Group, Period, Block 14, 5, p Appearance silvery lustrous gray Atomic mass 118. ... Hot metal work from a blacksmith Look up Metal in Wiktionary, the free dictionary. ...

Unlike neon and fluorescent lamps, EL lamps are not negative resistance devices so no extra circuitry is needed to regulate the amount of current flowing through them. In electrical circuits, static resistance is the ratio of the voltage across a circuit element to the current through it. ...

In principle, EL lamps can be made in any color but the greenish color most commonly used matches well with the peak sensitivity of human vision so it produces the greatest apparent light output for the least electrical power input.

See also

External links

Categories: Condensed matter stubs | Condensed matter physics | Electrical phenomena | Luminescence Lighting refers to either artificial light sources such as lamps or to natural illumination of interiors from daylight. ... A lamp, in technical usage, is a replaceable component such as an incandescent light bulb, which is designed to produce light from electricity. ... An incandescent light bulb and its glowing filament. ... An incandescent light bulb and its glowing filament. ... A Parabolic Aluminized Reflector light, or PAR light, is a type of light commonly used in motion picture production when a substantial amount of light is required for a scene. ... Image File history File links Download high resolution version (311x649, 278 KB) Summary I made this from an existing Public Domain JPEG. Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Spiral compact fluorescent light bulb A compact fluorescent lamp (CFL), also known as a compact fluorescent light bulb or an energy saving lightbulb, is a type of fluorescent lamp that screws into a regular light bulb socket or plugs into a small lighting fixture. ... A compact fluorescent lamp with an integrated electronic ballast A fluorescent lamp is a type of lamp that uses electricity to excite mercury vapor in argon or neon gas, resulting in a plasma that produces short-wave ultraviolet light. ... High-intensity discharge (HID) lamps include the types of electrical lights: mercury vapor, metal halide, high-pressure sodium and less common, xenon short-arc lamps. ... A Mercury-vapor lamp is a gas discharge lamp which uses mercury in an excited state to produce light. ... Metal halide lamps are similar to Mercury vapor lamps, but instead of just mercury, they also contain all metals in the halide group of the periodic table (Hence the name). ... Lighting neon lamp, two 220/230 volt and 110 V neon lamps and a screwdriver with neon lamp inside A neon lamp is a gas discharge lamp containing neon gas (or in types with different colors also other noble gas) at low pressure. ... A sodium vapor lamp is a gas discharge lamp which uses sodium in an excited state to produce light. ... The 300,000-watt Plasma Arc Lamp in the Infrared Processing Center (IPC) at Oak Ridge National Laboratory An arc lamp is a device that produces light by the sparking (or arcing, from voltaic arc or electric arc) of a high current between two carbon rod electrodes. ... Hydrargyrum Medium-Arc Iodide, frequently called just HMI is a mercury-halide discharge short arc lamp with a color temperature of approximately 5600K. The name is derived from Hydrargyrum, an archaic term for mercury while Iodide indicates that iodine is the halogen used to form the active compound. ... 15 kW Xenon short-arc lamp used in IMAX projectors Xenon arc lamps are an artificial light source. ... A Yablochkov candle (sometimes electric candle) is a type of electric carbon arc lamp, invented in 1876 by Pavel Yablochkov. ... Carbide lamps (acetylene lamps) are simple lamps that produce and burn acetylene by reacting calcium carbide with water. ... A collection of lit candles on ornate candlesticks A close-up image of a candle showing the wick and the various regions of the flame. ... Gas lighting is the process of burning piped natural gas or coal gas for illumination. ... Russian wick kerosene lamp. ... Limelight is a type of stage lighting once used in theatres and music halls. ... Antique bronze oil lamp with Christian symbol (replica) An oil lamp is a device used for lighting or for preserving a flame that is fueled by animal, vegetable or mineral oil. ... In contrast with all other electrical lamps that use electrical connections through the lamp envelope to transfer power to the lamp, in electrodeless lamps the power needed to generate light is transferred from the outside of the lamp envelope by means of (electro)magnetic fields. ... Blue, green and red LEDs. ... Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ... An eight-inch (20 cm) diameter plasma globe The effect of a conducting object (such as a hand) in close proximity to the plasma globe glass The central electrode of a plasma globe. ... Safety lamp is the name of a variety of lamps for safety in coal-mines against coal dust, methane, or firedamp, a highly explosive mixture of natural gas apt to accumulate in them. ...

Contents

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Examples of electroluminescent materials

Practical implementations

See also

External links

Mechanism