How LED Works
LEDs are the most significant technology disruption to the lighting industry since the invention of the incandescent lamp.
With incandescent lights, a tungsten filament is heated by electrical current until it glows or emits light. In a fluorescent lamp, an electric arc excites mercury atoms, which emit ultraviolet (UV) radiation. The phosphor coating on the inside of glass tubes converts UV radiation to visible light. In contrast, an LED is a semiconductor diode. It consists of a chip of semiconducting material treated to create a structure called a p-n (positive-negative) junction. When connected to a power source, current flows from the p-side or anode to the n-side, or cathode, but not in the reverse direction. Charge carriers (electrons and electron holes) flow into the junction from electrodes. When an electron meets a hole, it falls into a lower energy level and releases energy in the form of a photon (light). LEDs are noted for their exceptionally long-life, retaining 70% of their original output after 50-70,000 hours. The specific wavelength or color emitted by the LED depends on the materials used to make the diode. Red LEDs are based on aluminum gallium arsenide (AlGaAs). Blue LEDs are made from indium gallium nitride (InGaN) and green from aluminum gallium phosphide (AlGaP). "White" light is created by combining the light from red, green and blue (RGB) LEDs or by coating a blue LED with phosphor that converts the light to visible white light.
With incandescent lights, a tungsten filament is heated by electrical current until it glows or emits light. In a fluorescent lamp, an electric arc excites mercury atoms, which emit ultraviolet (UV) radiation. The phosphor coating on the inside of glass tubes converts UV radiation to visible light. In contrast, an LED is a semiconductor diode. It consists of a chip of semiconducting material treated to create a structure called a p-n (positive-negative) junction. When connected to a power source, current flows from the p-side or anode to the n-side, or cathode, but not in the reverse direction. Charge carriers (electrons and electron holes) flow into the junction from electrodes. When an electron meets a hole, it falls into a lower energy level and releases energy in the form of a photon (light). LEDs are noted for their exceptionally long-life, retaining 70% of their original output after 50-70,000 hours. The specific wavelength or color emitted by the LED depends on the materials used to make the diode. Red LEDs are based on aluminum gallium arsenide (AlGaAs). Blue LEDs are made from indium gallium nitride (InGaN) and green from aluminum gallium phosphide (AlGaP). "White" light is created by combining the light from red, green and blue (RGB) LEDs or by coating a blue LED with phosphor that converts the light to visible white light.
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