The working principle of LED

LED, like ordinary diodes, are composed of a PN junction and also have single conductivity. When a forward voltage is applied to the LED, the holes injected from the P region into the N region and the electrons injected from the N region into the P region recombine with the electrons in the N region and the holes in the P region within a few micrometers near the PN junction, producing spontaneous emission fluorescence. The energy states of electrons and holes in different semiconductor materials are different. When electrons and holes recombine, the amount of energy released varies. The more energy released, the shorter the wavelength of the light emitted. Commonly used are diodes that emit red, green, or yellow light. The reverse breakdown voltage of LED is greater than 5 volts. Its forward volt ampere characteristic curve is very steep, and when used, a current limiting resistor must be connected in series to control the current passing through the diode.