LED lighting principles
LED (LightingEmittingDiode) lighting that is LED lighting, is a semiconductor solid-state light-emitting devices. It is the use of solid semiconductor chip as luminescent materials in the semiconductor carrier recombination occurs through the release of excess energy photon emission caused, directly emit red, yellow, blue, green, blue, orange, purple, white light. LED lighting products is the use of LED as a light source created by the lighting apparatus.
LED is driven by Ⅲ - Ⅳ compounds, such as GaAs (gallium arsenide), GaP (gallium phosphide), GaAsP (gallium arsenide phosphorus) and other semiconductor made of, its core is the PN junction. So it is generally Mitutoyo PN junction photovoltaic I-N characteristic, namely the forward, reverse blocking, breakdown characteristics. In addition, under certain conditions, it has an emission characteristic. In the forward voltage, electrons injected from the N region P area, the hole injection from the P region N region. Enter each zone minority carriers (minority carriers) portion of the majority carrier (more children) composite and light.
Assuming luminescence occurs in the P region, then the injected electrons and valence band holes direct composite and light, or luminescence center was first captured, and then with hole recombination luminescence. In addition to this light-emitting compound, some electrons are non-luminescent center (the center between the conduction band, dielectric belt near the middle) to capture, and then with hole recombination, each time the energy released is not, can not form a visible light. Glowing compound relative to the non-emitting composite volume ratio of the amount the greater the higher quantum efficiency. Since the composite is glowing in the minority carrier diffusion region, so light only near the PN junction faces μm or less produced.
Theory and Practice shows that the peak wavelength λ of the light emitting region of the semiconductor forbidden band width Eg related materials, which
λ ≈ 1240/Eg (mm)
Eg the formula units of electron volts (eV). If visible light (wavelength of 380nm ~ 780nm violet red), Eg of the semiconductor material should be between 3.26 ~ 1.63eV. Longer wavelength than the red light to infrared light. Now has infrared, red, yellow, green and blue light emitting diodes, but blue diode cost, price, use not widespread.
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