In 1960s, scientists and technicians developed a LED light emitting diode, using the principle of semiconductor pn junction luminescence. The LED, which was developed at the time, was used as a material for GaASP, and its luminous color was red. After nearly 30 years of development, everyone is very familiar with the LED, has been able to send a variety of color red, orange, yellow, green, blue and so on. However, the white light, which is needed for lighting, has only been developed since 2000. Here we introduce the reader to the white light LED for lighting.
The earliest use of the LED light source made from the principle of semiconductor P-N junction luminescence came out in the early 1960s. The material used at that time is GaAsP, emitting red light (lambda p=650nm). When driving current is 20 mA, the luminous flux is only a few thousand lumens, and the corresponding luminous efficiency is about 0.1 lumen / tile.
In the middle of 70s, the elements In and N were introduced to make LED produce green light (lambda p=555nm), yellow light (lambda p=590nm) and orange light (lambda p=610nm), and the luminous efficiency also increased to 1 lumens / tiles.
By the beginning of 80s, the LED light source of GaAlAs was presented, making the optical visual efficiency of the red LED up to 10 lumens / watts.
At the beginning of 90s, the successful development of the red and yellow light greenish blue, GaAlInP and GaInN two kinds of new materials, the LED luminous efficiency is improved greatly.
In 2000, the luminous efficiency of LED made in the former area was 100 lumens / tile in red and orange area (lambda p=615nm). The luminous efficiency of LED made in the green area (lambda p=530nm) could reach 50 lumens / watts.
If the energy saving lamp is frequently started or turned off
Principle of LED lamp