The semiconductor wafer consists of two parts, one is a P-type semiconductor, in which holes are dominant, and the other is an N-type semiconductor, mainly electrons. But when these two semiconductors are connected together, a pn junction is formed between them.
When the current acts on the chip through the wire, the electrons will be pushed to the P region, where the electrons will recombine with holes, and then the energy will be emitted in the form of photons, which is the principle of LED light emission. The wavelength of light, that is, the color of light, is determined by the material forming the pn junction.
LED can directly emit red, yellow, blue, green, cyan, orange, purple and white light.
Extended data
For conventional LED lamps, the peak value of the light source is basically in the range of 450~470 nm, and the illuminance of the conventional light environment generally does not exceed 600 lux (light intensity unit), and the lamp is packaged outside the LED light source. Therefore, most LED lamps produced by regular manufacturers will not cause harm to the retina.
According to the domestic Blu-ray safety standards, both Class 0 (no harm) and Class 1 (low harm) products can be used, and Class 0 products should be used by special people such as infants. When purchasing LED lamps, you should look for the products of regular manufacturers, choose soft and warm yellow lights, and the indoor lighting color temperature should not exceed 4000 Kelvin (K).
When you use it at home, you should lower the lampshade to ensure that the light of the book or desktop is suitable, and at the same time block the light source to avoid glare; When you turn on the desk lamp, you'd better turn on other lamps to make the indoor light relatively harmonious.
Baidu encyclopedia -LED lamp
People's Network-Use LED lights to prevent blue light from hurting eyes.