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Led Lighting Principle
Author:admin Hit: Date:2016-9-27 16:49:55

LED Lighting principle

 LED light source is made of Ⅲ-Ⅳ compounds, such as GaAs (gallium arsenide), GaP (gallium phosphide), GaAsP (gallium arsenide phosphorus) and other semiconductor , its core is the PN junction. I-V characteristics so that it has a general P-N junction, namely the forward pass, reverse cut-off, breakdown characteristics. In addition, under certain conditions, it also has luminescent properties. In the forward voltage, electrons injected from the N area P area, hole injection from the P region N region. Into other areas of minority carriers (minority) part of the majority carrier (more children) composite and light.

Suppose emitting occurred in the P region, the injected electrons and valence band holes direct composite and light, or luminescence center was first captured, then with the hole recombination luminescence. In addition to this light-emitting compound, some electrons are (between the center of the conduction band, medium band near the middle) to capture the non-luminescent center, and then with the hole recombination, each time the energy released is not, can not form visible. Emitting composite volume with respect to the non-light emitting compound ratio of the amount, the higher the quantum efficiency. Since the composite is in the minority carrier diffusion area glowing, it produces only light near the PN junction within a few μm.

Theory and Practice shows that the peak wavelength λ of the semiconductor light-emitting material band gap Eg relevant area, namely λ≈1240 / Eg (mm)Eg formula units of electron volts (eV). If you can produce visible light (wavelength of 380nm ~ 780nm violet red), Eg of semiconductor materials should be between 3.26 ~ 1.63eV. Longer wavelength than red light to infrared light. Existing infrared, red, yellow, green and blue light-emitting diodes, but the blue diode cost, the price is high, use not common.