The first application of light-emitting LED light source that that made of the principles of PN junction semiconductor came in the early 1960s. The material is GaAsP, lighting hair red (λp = 650nm). When the drive current is 20 mA, the luminous flux is only a few parts per thousand lumens; the corresponding luminous efficiency is about 0.1 lumens / watt.
Mid-1970s, the elements of In and N were introduced, which cause that LED can produces green (λp = 555nm), yellow (λp = 590nm) and orange (λp = 610nm) light. The luminous efficiency of LED light is also increased to 1 lumen / watt.
By the early 1980s, there has been GaAlAs LED light source; so that the red LED light efficiency has up to 10 lumens / watt.
Early 1990s, the successful development of two new materials: GaAlInP that can emit red light, yellow light and the GaInN that emits hair green and blue make LED light efficiency has been greatly improved. In 2000, in red, orange area (λp = 615nm), the luminous efficiency of the LED that made of former up to 100 lm / W, while in the green zone (λp = 530nm), that of the latter can reach 50 lm / watts.
Monochromatic LED Applications
Originally, the LED was used as the indication light of the instruments then a variety of light-colored LED has been widely used in traffic lights and a large area of the display, resulting in a good economic and social benefits. Take the 12 inches of red traffic lights for example, in the United States, the long-life, low-efficiency 140-watt incandescent lamp is used as a light source, which produces 2000 lumens of white light. Through red filter, the light loss of 90%, only 200 lumens of red light are left. In the new design of the lamp, MyLED adopted the 18 red LED light sources, including circuit losses, including a total power consumption of 14 watts to produce the same light effect.
LED lights are also important areas of automotive light applications. In 1987, China began installing brake light in the car, because the LED fast response (nanosecond) which let the driver know that the trailing vehicle driving conditions earlier, reducing the incidence of rear-end accidents.
In addition, LED lights have been applied on the outdoor red, green, blue full-color display, miniature flashlight key chain and other areas. anty881209wong 140403