"Light Emitting Diodes (LEDs) are optoelectronic devices made of three-five group compound semiconductors, and their core is a PN junction.

Under the forward voltage, electrons are injected from the N area into the P area, and holes are injected from the P area into the N area. Part of the minority carriers and majority carriers that enter the opposing area recombine and emit light.

The nature of the material forming the PN junction (band gap) determines the wavelength of the emitted light. For visible light, it determines the color of the light.

The main characteristics of 　　LED are: small size, low power consumption, long service life, high brightness and low heat, environmental protection and durability.

Working under proper current and voltage, the life span of the LED can be as long as 100,000 hours.

Classification and application of LED

　　 According to the type of light emitted, LEDs can be divided into visible light LEDs and invisible light LEDs.

　　Visible LEDs include red, orange, yellow, green, blue, and violet LEDs. Among them, red LED materials are mainly GaP (binary system), AlGaAs (ternary system) and AlGaInP (quaternary system); blue/white LED materials are mainly GaN.