The earliest use of semiconductor n junction light-emitting Principle made of LED light source was published in the early 1960s. At that time, the material used was gaasp, red Light (λp=650nm), in the driving current of 20 ma, luminous flux only a few lumens, the corresponding optical visual performance of about 0.1 lumens/watts.
In the mid 70, the introduction of elements in and N, led to the production of green light (λp=555nm), yellow (λp=590nm) and orange Light (λp=610nm), light visual efficiency also increased to 1 lumens/watts.
By the early 80, there was a gaalas LED light source, which made the red LED's optical viewing efficiency reach 10 lumens/watts.
The early 90, red, yellow gaalinp and green, Blue Gainn Two of new materials developed successfully, so that led light visual performance has been greatly improved.
In 2000, the former led in the Red and Orange region (λp=615nm) of light efficiency reached 100 lumens/watts, while the latter made of led in the green area (λp=530nm) Optical visual performance can reach 50 lumens/watts.