The earliest LED light source based on the principle of semiconductor pn junction was produced in the early 1960s. The material used at that time was GaAsP, which emitted red light (λp=650nm). When the driving current is 20 mA, the luminous flux is only a few thousandths of lumens, and the corresponding luminous efficiency is about 0. 1 lumen/watt.

In the mid-1970s, the introduction of In and N elements led to green light (λp=555nm), yellow light (λp=590nm) and orange light (λp=6 10nm), and the light efficiency was also improved to 1 lumen/watt.

In the early 1980s, GaAlAs LED light source appeared, which made the light efficiency of red LED reach 10 lumen/watt.

In the early 1990s, two new materials, GaAlInP emitting red and yellow light and GaInN emitting green and blue light, were successfully developed, which greatly improved the light efficiency of LED. In 2000, the light efficiency of the LED manufactured by the former reached 100 lumens/watt in red and orange regions (λp=6 15nm), while the light efficiency of the LED manufactured by the latter reached 50 lumens/watt in green regions (λp=530nm).