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Light Emitting Diodes

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A light-emitting diode consists of multiple layers of semi-conducting material. If the diode is operated with direct current, the active layer generates light. The resulting light is decoupled directly or by reflection. Unlike incandescent light bulbs, which emit a continuous spectrum, LEDs emit light in a specific colour. The colour of the light depends on the semi conductive material used. Mainly two material systems (AllnGaP and InGaN) are used in order to produce LEDs with high brightness levels in all colours from blue to red as well as white (produced by luminescence conversion). Different voltages are needed in order to operate the diode in a forward direction.

LEDs are semiconductor crystals. According to the composition of the crystalline structures, they emit red, green, yellow or blue light when electric current flows through them. Blue LEDs can also generate white light by means of an additional yellow luminescent layer (luminescence conversion). Another way to generate white light is to mix red, green and blue light. This method is mainly used when the overall aim is not the generation of white light, but the generation of decorative lighting effects using various rich colours.



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