LED basics: measurement of light color [detailed illustration]

I. Introduction

As an emerging illuminator, light-emitting diodes ( LEDs ) have the advantages of high electro-optic efficiency, small size, long life, low voltage, energy saving and environmental protection. They are the best choice for next-generation lighting devices. The development of LED has received widespread attention at home and abroad, and new products and technologies are emerging. In recent years, the LED industry has developed rapidly, the light efficiency has been increasing, and the brightness has been continuously improved. Nowadays, LED has penetrated into a large number of applications, especially the continuous improvement of white LED technology , and the application of LED in the field of lighting has become more and more popular.

Figure 1: The development of the LED industry

1, the working principle of LED

A light-emitting diode (LED) is a solid device that converts electrical energy into light energy. Its structure is mainly composed of a PN junction chip, an electrode, and an optical system. The basic working principle of LED is an electro-optical conversion process. When a forward bias is applied to both ends of the PN junction, the positive charge of the P region will diffuse to the N region due to the decrease of the PN junction barrier, and the electrons in the N region also The P region diffuses while forming an accumulation of non-equilibrium charges in the two regions. Since the minority carriers generated by current injection are unstable, for the PN junction system, the non-equilibrium holes injected into the valence band are combined with the electrons in the conduction band, and the excess energy will be radiated outward in the form of light. The greater the energy difference between electrons and holes, the higher the energy of the photons produced. The energy level difference is different, the frequency and wavelength of the generated light are different, and the color of the corresponding light is different.

Figure 2: How LEDs work

2, LED light parameters

Figure 3: Main light parameters of the LED