Braunstein observed infrared emission generated by simple diode structures using gallium antimonide (GaSb), GaAs, indium phosphide (InP), and silicon-germanium (SiGe) alloys at room temperature and at 77 kelvins. Rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide (GaAs) and other semiconductor alloys in 1955. Kurt Lehovec, Carl Accardo, and Edward Jamgochian explained these first LEDs in 1951 using an apparatus employing SiC crystals with a current source of a battery or a pulse generator and with a comparison to a variant, pure, crystal in 1953. Hungarian Zoltán Bay together with György Szigeti pre-empted LED lighting in Hungary in 1939 by patenting a lighting device based on silicon carbide, with an option on boron carbide, that emitted white, yellowish white, or greenish white depending on impurities present. Destriau worked in the laboratories of Madame Marie Curie, also an early pioneer in the field of luminescence with research on radium. In his publications, Destriau often referred to luminescence as Losev-Light. In 1936, Georges Destriau observed that electroluminescence could be produced when zinc sulphide (ZnS) powder is suspended in an insulator and an alternating electrical field is applied to it. His research was distributed in Soviet, German and British scientific journals, but no practical use was made of the discovery for several decades, partly due to the very inefficient light-producing properties of silicon carbide, the semiconductor Losev used. Russian inventor Oleg Losev reported the creation of the first LED in 1927. Round of Marconi Labs, using a crystal of silicon carbide and a cat's-whisker detector. History Discoveries and early devices Green electroluminescence from a point contact on a crystal of SiC recreates Round's original experiment from 1907.Įlectroluminescence as a phenomenon was discovered in 1907 by the English experimenter H. In exchange for these generally favorable attributes, disadvantages of LEDs include electrical limitations to low voltage and generally to DC (not AC) power, inability to provide steady illumination from a pulsing DC or an AC electrical supply source, and lesser maximum operating temperature and storage temperature.Īs a transducer of electricity into light, LEDs operate in reverse of photodiodes. LEDs have many advantages over incandescent light sources, including lower power consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. LEDs have also given rise to new types of displays and sensors, while their high switching rates are useful in advanced communications technology with applications as diverse as aviation lighting, fairy lights, strip lights, automotive headlamps, advertising, general lighting, traffic signals, camera flashes, lighted wallpaper, horticultural grow lights, and medical devices. Later developments produced LEDs available in visible, ultraviolet (UV), and infrared wavelengths, with high, low, or intermediate light output, for instance white LEDs suitable for room and outdoor area lighting. The first visible-light LEDs were of low intensity and limited to red.Įarly LEDs were often used as indicator lamps, replacing small incandescent bulbs, and in seven-segment displays. Infrared LEDs are used in remote-control circuits, such as those used with a wide variety of consumer electronics. Īppearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared (IR) light. White light is obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device. The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. A bulb-shaped modern retrofit LED lamp with aluminum heat sink, a light diffusing dome and E27 screw base, using a built-in power supply working on mains voltageĪ light-emitting diode ( LED) is a semiconductor device that emits light when current flows through it. Close-up image of a surface mount LED Close-up of an LED with the voltage being increased and decreased to show a detailed view of its operation. The flat bottom surfaces of the anvil and post embedded inside the epoxy act as anchors, to prevent the conductors from being forcefully pulled out via mechanical strain or vibration.
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