The Working Principle Of Light-emitting Diodes
Feb 20, 2021
Like ordinary diodes, light-emitting diodes are composed of a PN junction, and they also have unidirectional conductivity.
When the forward voltage is applied to the light-emitting diode, the holes injected from the P area to the N area and the electrons injected from the N area to the P area are respectively in contact with the electrons in the N area and the voids in the P area within a few microns of the PN junction. The holes recombine and produce spontaneous emission fluorescence. The energy states of electrons and holes in different semiconductor materials are different. When electrons and holes recombine, the energy released is somewhat different.
The more energy released, the shorter the wavelength of the emitted light. Commonly used are diodes that emit red, green or yellow light. The reverse breakdown voltage of the light-emitting diode is greater than 5 volts. Its forward volt-ampere characteristic curve is very steep, and a current-limiting resistor must be connected in series to control the current through the diode.
