The development of LED lights
First semiconductor p-n junction light emitting principle LED light source come out in in the early 1960 of the 20th century. Materials used at the time was GaAsP, glow (λ p=650nm), when the current is 20 Ma, luminous flux only few thousandths lumens, about 0.1 lumens/w luminous efficacy.
The mid-70, introducing elements In n, make the LED green light (λ p=555nm), yellow (λ p=590nm) and orange (λ p=610nm), luminous efficacy is increased to 1 lumen/Watt.
To the early 80 's, appeared GaAlAs LED light source red LED luminous efficacy up to 10 lumens/Watt.
Beginning of the 90, GaAlInP of red, yellow and green, Blu-ray GaInN both development of new materials for success, the LED luminous efficiency is greatly improved.
In 2000, which LED in red, made of Orange (λ p=615nm) up to 100 lumens/Watt luminous efficiency, which LED in the Green region made of (λ p=530nm) luminous efficacy can be up to 50 lumens per watt.