Origin of Folding
In the 1960s, scientific and technological workers used the principle of semiconductor PN junction light to develop LED light-emitting diodes. The LED developed at that time was made of GaASP, and its light-emitting color was red. After nearly 30 years of development, the LED, which everyone is very familiar with, can emit red, orange, yellow, green, blue and other colors. However, white LEDs for lighting have only been developed after 2000. This article introduces readers to white LEDs for lighting.
The first LED light source made using the principle of semiconductor P-N junction light emission came out in the early 1960s. The material used at that time was GaAsP, which emits red light (λp=650nm). When the driving current is 20 mA, the luminous flux is only a few thousandths of lumens, and the corresponding optical efficiency is about 0.1 lumens/watt.
In the mid-1970s, the elements In and N were introduced to make the LED produce green light (λp=555nm), yellow light (λp=590nm) and orange light (λp=610nm), and the optical efficiency was increased to 1 lumens/watt.
In the early 1980s, GaAlAs LED light sources appeared, making the luminous efficacy of red LEDs reach 10 lumens/watt.
In the early 1990s, the successful development of two new materials, GaAlInP, which emits red and yellow light, and GaInN, which emits green and blue light, greatly improved the optical efficiency of LEDs.
In 2000, the LED made by the former had a luminous efficiency of 100 lumens per watt in the red and orange zone (λp=615nm), while the LED made by the latter had a luminous efficiency of 50 lumens in the green zone (λp=530nm). /watt.