Elsevier Science. August 1, 2025. p > 자유게시판

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A mild-emitting diode (LED) is a semiconductor device that emits light when present flows via it. Electrons in the semiconductor recombine with electron holes, releasing energy within the type of photons. The color of the sunshine (corresponding to the vitality of the photons) is set by the vitality required for electrons to cross the band hole of the semiconductor. White mild is obtained through the use of multiple semiconductors or a layer of mild-emitting phosphor on the semiconductor gadget. Showing as practical digital parts in 1962, the earliest LEDs emitted low-depth infrared (IR) mild. Infrared LEDs are utilized in remote-management circuits, such as those used with a wide number of consumer electronics. The first seen-mild LEDs have been of low intensity and limited to purple. Early LEDs had been often used as indicator lamps, changing small incandescent bulbs, and in seven-phase displays. Later developments produced LEDs available in seen, ultraviolet (UV), and infrared wavelengths with excessive, low, or intermediate mild output; for instance, white LEDs appropriate for room and outside EcoLight home lighting.

LEDs have also given rise to new forms of displays and sensors, while their excessive switching rates have makes use of in superior communications expertise. LEDs have been used in various functions corresponding to aviation lighting, fairy lights, strip lights, automotive headlamps, promoting, stage lighting, common lighting, traffic alerts, digital camera flashes, lighted wallpaper, EcoLight horticultural grow lights, and EcoLight home lighting medical devices. LEDs have many benefits over incandescent light sources, together with lower energy consumption, a longer lifetime, improved physical robustness, EcoLight smaller sizes, and quicker switching. In exchange for these typically favorable attributes, disadvantages of LEDs include electrical limitations to low voltage and customarily to DC (not AC) power, the lack to offer regular illumination from a pulsing DC or an AC electrical provide source, and a lesser most operating temperature and storage temperature. LEDs are transducers of electricity into gentle. They operate in reverse of photodiodes, which convert mild into electricity. Electroluminescence from a strong state diode was discovered in 1906 by Henry Joseph Round of Marconi Labs, and was printed in February 1907 in Electrical World.

Round noticed that various carborundum (silicon carbide) crystals would emit yellow, mild inexperienced, orange, or blue gentle when a voltage was handed between the poles. From 1968, commercial LEDs were extraordinarily costly and saw no practical use. Within the early 1990s, Shuji Nakamura, Hiroshi Amano and Isamu Akasaki developed blue gentle-emitting diodes that had been dramatically extra efficient than their predecessors, EcoLight bringing a brand new generation of shiny, power-efficient white lighting and full-colour LED displays into practical use. For this work, they gained the 2014 Nobel Prize in Physics. In a gentle-emitting diode, the recombination of electrons and electron holes in a semiconductor produces mild (infrared, visible or UV), a process called electroluminescence. The wavelength of the sunshine is determined by the power band gap of the semiconductors used. Since these materials have a high index of refraction, design options of the gadgets corresponding to particular optical coatings and die shape are required to effectively emit mild. Not like a laser, the sunshine emitted from an LED is neither spectrally coherent nor even extremely monochromatic.

Its spectrum is sufficiently slim that it seems to the human eye as a pure (saturated) color. Additionally not like most lasers, its radiation will not be spatially coherent, so it can't approach the very excessive intensity characteristic of lasers. By selection of different semiconductor materials, single-shade LEDs can be made that emit mild in a slender band of wavelengths, from the near-infrared by the visible spectrum and into the ultraviolet range. The required working voltages of LEDs enhance as the emitted wavelengths turn out to be shorter (higher energy, purple to blue), because of their rising semiconductor band hole. Blue LEDs have an lively region consisting of one or more InGaN quantum wells sandwiched between thicker layers of GaN, called cladding layers. By varying the relative In/Ga fraction within the InGaN quantum wells, the light emission can in idea be diverse from violet to amber. Aluminium gallium nitride (AlGaN) of varying Al/Ga fraction can be utilized to manufacture the cladding and quantum effectively layers for ultraviolet LEDs, but these gadgets haven't but reached the level of effectivity and technological maturity of InGaN/GaN blue/green devices.

If unalloyed GaN is used on this case to type the active quantum properly layers, the machine emits near-ultraviolet mild with a peak wavelength centred round 365 nm. Inexperienced LEDs manufactured from the InGaN/GaN system are way more environment friendly and brighter than inexperienced LEDs produced with non-nitride material techniques, however sensible gadgets nonetheless exhibit effectivity too low for top-brightness applications. With AlGaN and AlGaInN, even shorter wavelengths are achievable. Close to-UV emitters at wavelengths round 360-395 nm are already low-cost and sometimes encountered, for example, as black mild lamp replacements for inspection of anti-counterfeiting UV watermarks in documents and financial institution notes, and for UV curing. Considerably more expensive, shorter-wavelength diodes are commercially accessible for wavelengths down to 240 nm. As the photosensitivity of microorganisms approximately matches the absorption spectrum of DNA, with a peak at about 260 nm, UV LED emitting at 250-270 nm are anticipated in potential disinfection and sterilization devices. Recent research has proven that commercially available UVA LEDs (365 nm) are already effective disinfection and sterilization devices.