Light-emitting diode is called led for short. Made of compounds containing gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N), etc.
When electrons recombine with holes, they can emit visible light, so they can be used to make light-emitting diodes. Used as an indicator light in circuits and instruments, or as a text or digital display. Gallium arsenide diodes emit red light, gallium phosphide diodes emit green light, silicon carbide diodes emit yellow light and gallium nitride diodes emit blue light. Because of its chemical properties, it can be divided into organic light-emitting diode and inorganic light-emitting diode LED.
Principle:
It is a semiconductor diode, which can convert electric energy into light energy. Light-emitting diodes, like ordinary diodes, are composed of PN junctions and also have unilateral conductivity. When a DC voltage is applied to the LED, holes injected from the P region to the N region and electrons injected from the N region to the P region recombine with the electrons in the N region and the P region within a few microns near the PN junction, respectively, resulting in spontaneous 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 is released, the shorter the wavelength of light is. Diodes that emit red, green or yellow light are commonly used. The reverse breakdown voltage of LED is greater than 5 volts. Its forward volt-ampere characteristic curve is very steep, and a current limiting resistor needs to be connected in series to control the current through the diode.