The terminal voltage of the PN junction of the led lamp bead constitutes a certain potential barrier. When the forward bias voltage is applied, the potential barrier drops, and the majority carriers in the P region and the N region diffuse to each other. Since the electron mobility is much larger than the hole mobility, a large number of electrons will diffuse into the P region, which constitutes the injection of minority carriers into the P region. These electrons recombine with holes in the valence band, and the energy obtained during recombination is released in the form of light energy. This is the principle of PN junction light emission.