What is the development and application for LED Photochromic ?

It has been a long history to adopt LED as lighting source, now let us talk about the LED photochromic.

What is the categories and developing history of LED Homogeneous Light ?
The earliest LED lighting source which was made by semiconductor P-N junction appeared in the 1960s. At that time, its material is GaAsP, it is red color lighting (λp=650nm), its luminous flux is just some of thousand percentage lumen when the driving current is 20mA, its relative lighting-effectiveness is about 0.1LM/W.

In the mid-1980s, the LED lighting source of GaAlAs appeared, which is to make the lighting-effectiveness of red color be up to 10LM/W.

In 1990s, The successful research of GaAlInP which bright red and yellow lighting color and GaInN which bright blue lighting, has made the lighting-effectiveness of LED great improvement. In 2000, the lighting-effectiveness which was made by former materials can reach 100LM/W in the field of Red and orange (λp=615nm), the lighting-effectiveness which was made by the later materials can reach 50LM/W in the field of green (λp=530nm).

What is the application of LED homogeneous light ?
Initially, LED was applied as indicator lighting source for instruments and meters, then various of photochromic LED has widely applied for traffic light and large area monitor, which has produced great economic benefits and social benefits. Taking 12inch red lighting color traffic light as example, at past, USA was to adopt longevity lamp with low lighting-effectiveness incandescent lamp whose power is 140W, it can produce 200LM white color. After getting through filter, the lighting-consumption is 90%, just remain 200LM red lighting. In the new design lamp, Lumileds company adopted 10pcs red LED lighting sources, its total power consumption is 14W which has included circular wastage, it can produce the same lighting-effectiveness.

Automobile signal lamp is one of important application fields for LED lighting source. In 1987, China started to install high place brake light in automobile, as the LED response is fast (some nanosecond), it can early let the closing driver to know its driving state, to reduce pileup incident.
In addition, LED lamp also got application in outdoor monitor whose color is red, green and blue, micro spotlight, etc.

The Research and Development of White Color LED.
In terms of usual illumination, human prefer to require whit color lighting source. The white color LED was successfully researched in 1998. This kinds of LED is to seal GaN chip and YAG integrated. GaN chips bright blue lighting (λp=465nm, Wd=30nm), YAG fluorescent powder which was made by high temperature Ce3+ bright yellow lighting beam after being stimulated by this blue lighting, its peak is 550nm. The blue LED substrate was installed in the side of reflection cavity, to cover resin film which has YAG, it is about 200-500nm. The blue lighting part which is brightened by LED substrate is absorbed by fluorescent powder, another blue lighting mix with the yellow lighting which is brightened by fluorescent powder, it can get white color lighting. Presently, In terms of InGaN/YAG white LED, the various lightings whose color temperature is 3500K-10000K can be got by changing the chemical component of YAG fluorescent powder and adjusting the thickness of fluorescent powder.

Above is to introduce some basic knowledge for LED which has been widely applied for many fields in our daily lives. Especially for solar lighting products, LED has become an essential lighting source.

Bingsolar Power, 27th, July, 2018