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What is the working principle of LED?
Return list Source: 未知 Release date: 2019-12-29

LED is a kind of commonly used light-emitting device. It is widely used in the field of lighting because of the compound release of energy by electrons and holes. [LED can efficiently convert electric energy into light energy, which has a wide range of uses in modern society, such as lighting, flat panel display, medical devices, etc. So, how does it work? Let Jin Youheng elaborate:
Working principle of LED:
The light-emitting diode is composed of a PN junction like the common diode, and also has the single guide property. When a positive voltage is applied to the LED, the holes injected from the P-region to the N-region and the electrons injected from the N-region to the P-region are combined with the electrons in the N-region and the holes in the P-region within a few microns near the PN junction, respectively, to produce spontaneous emission fluorescence. The energy states of electrons and holes are different in different semiconductor materials. When electrons and holes compound, the amount of energy released is different. The more energy released, the shorter the wavelength of light. Commonly used are red, green or yellow diodes. The reverse breakdown voltage of the LED is greater than 5 v. Its forward V-A characteristic curve is very steep, so the current limiting resistor must be connected in series to control the current passing through the diode.
The core of LED is composed of p-type semiconductor and n-type semiconductor. There is a transition layer between p-type semiconductor and n-type semiconductor, called PN junction. In the PN junction of some semiconductor materials, when the injected minority carrier and the majority carrier are combined, the excess energy will be released in the form of light, so that the electric energy can be directly converted into light energy. When the PN junction is applied with reverse voltage, a few carriers are difficult to inject, so it does not emit light. When it is in a positive working state (i.e. positive voltage is applied at both ends), when the current flows from the LED anode to the cathode, the semiconductor crystal emits different colors of light from ultraviolet to infrared. The intensity of light is related to the current.

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