The basic working principle of LED is an electro-optical conversion process. When a forward bias is applied across the PN junction, the positive charge in the P region will diffuse toward the N region due to the lowering of the PN junction barrier, and the electrons in the N region also The P region diffuses while forming an accumulation of non-equilibrium charges in the two regions. Because the minority carriers generated by current injection are relatively unconstrained, for the PN junction system, the non-equilibrium holes injected into the valence band are combined with the electrons in the conduction band, and the excess energy will be radiated outward in the form of light.
The greater the energy difference between electrons and holes, the higher the photon energy produced. The energy level difference is different, the frequency and wavelength of the generated light are different, and the corresponding light color will be different.