The development of LED lamps has gone through five stages:
One: In the 1960s, people learned the basics of semiconductor materials that can produce light, and the first commercial LED diodes were produced in 1960.
Two: The core part of the light-emitting diode is a wafer composed of p-type semiconductors and n-type semiconductors. There is a transition layer between p-type semiconductors and n-type semiconductors, called p-n junction.
Elements In and N were introduced in the mid-1970s, enabling LED lights to produce green, yellow, and orange light, and their luminous efficiency increased to 1 lumen/watt.
Three: In 1989, white LED lamps were successfully developed.
The LED is packaged with a GaN chip and aluminum garnet (YAG).
The GaN chip emits blue light (λp=465nm, Wd=30nm). After the YAG with Ce3+ content made by high temperature sintering is stimulated by this blue light, the phosphor emits yellow light with a peak value of 550nm.
Four: In 1993, Japan Nakamura Shuji successfully developed a high-brightness blue light-emitting diode.
Compared with traditional fluorescent lamps and incandescent bulbs, LEDs are not only small in size, environmentally friendly, power-saving, and have a lifespan of up to 100,000 hours. Light-emitting diodes have jumped to become a new light source for lighting and displays in the 21st century.
5: On October 13, 2018, the team of academicians Huang Wei and Wang Jianpu of the Chinese Academy of Sciences increased the external quantum efficiency of perovskite light-emitting diodes (LEDs) to 20.7%, nearly half of that of international counterparts. ” published on.