How do light-emitting diodes emit light?

The fundamental principle is the energy level transition of electrons!
The electron in an atom has many energy levels. When the electron jumps from a high energy level to a low energy level, the energy of the electron is reduced, and the reduced energy is converted into a photon and emitted. A lot of these photons are lasers.
The principle of LED is similar. However, the difference is that the LED does not emit light through the transition of electrons inside the atom, but by applying a voltage across the PN junction of the LED, the PN junction itself forms an energy level (in fact, a series of energy Level), and then electrons jump at this energy level and produce photons to emit light.DE Full Spectrum Hydroponics Grow Lights
Light-emitting diodes are simply referred to as LEDs. A diode made of a compound of gallium (Ga), arsenic (AS), and phosphorus (P) can radiate visible light when electrons and holes recombine, so it can be used to make light-emitting diodes, which can be used as indicators in circuits and instruments Light, or compose text or digital display. Phosphorus gallium arsenide diodes emit red light, gallium phosphide diodes emit green light, and silicon carbide diodes emit yellow light.
It is a type of semiconductor diode that can convert electrical energy into light energy; often abbreviated as LED. Like ordinary diodes, light-emitting diodes are composed of a PN junction, and they also have unidirectional conductivity. When a 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 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.