How Light Emitting Diodes (LEDs) Emit Light

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LEDs, or light-emitting diodes, are semiconductor solid-state lighting devices that produce light through the release of energy from the combining of electrons and holes.

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LEDs can be classified into different types based on the semiconductor material used, the light-emitting principle, and each type is capable of emitting a specific wavelength of light to produce different colors.

LED in common colors:

Red LEDs: These LEDs are usually made of materials such as Aluminum Gallium Arsenide (AlGaAs) or Gallium Arsenide Phosphorus (GaAsP), which emit red light through electron leaps.

Green LEDs: Green LEDs use Gallium Nitride (GaN) material to produce green light.

Blue LEDs: Blue LEDs use Indium Gallium Nitride (InGaN) material to produce blue light.

White LEDs: White LEDs are usually achieved by adding a phosphor layer to a blue LED. The blue LED excites the phosphor to emit yellow light, which is combined to produce white light.

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LED uses a solid semiconductor chip as the light emitting material, in which excess energy in the semiconductor is released by binding carriers (electrons and holes), causing photon emission. This process can directly emit light in the primary colors of red, yellow, blue and green. The basic structure of an LED is a piece of electroluminescent semiconductor material, usually mounted on a board with leads and surrounded by an epoxy resin seal to protect the internal chip.

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The core of an LED is a wafer of a P-type semiconductor and an N-type semiconductor, with a PN junction formed between them. When a positive voltage is applied to the LED, electrons flow from the N-type semiconductor to the P-type semiconductor, while holes flow from the P-type semiconductor to the N-type semiconductor. When these electrons and holes meet and combine near the PN junction, energy is released and emitted as photons. The color of the light emitted by the LED is determined by the material of the PN junction, because different materials have different energy level differences that affect the wavelength of photons emitted when electrons and holes combine.

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