White-ray LEDs are actually made by blue LEDs: as the name implies, blue LED will generate blue rays. After YAG phosphor powder, these blue rays will transform into yellow rays. And the combination of blue rays and yellow rays (in a certain proportion) will create white rays. White-ray LED lights are widely used in various white lighting and backlighting applications. This type of white light was also defined as solid white lighting, having three major features: small size, energy saving, long service life. But compare with traditional fluorescent tubes, these lamps have a much lower lighting efficiency. Photonic crystals are an effective solution for this problem.
In order to solve the low lighting efficiency of Blue-ray LEDs, scientists infused photonic crystals into Blue-ray LEDs to create a new compound: Photonic Crystal Blue-ray LED. Traditional manufacturing process of LED is rather simple. But the point is their low lighting efficiency. Because of the total reflection of the surface of traditional Blue-ray LEDs, rays came out from active layers will be totally reflected by the reflecting surface.
Aiming at this problem, CREE made some enhancements in the production process. A tiny slope beside the active layer can be seen in each deformed chip. Light efficiency can be dramatically improved by adding these slopes. Another improvement is designing a secondary set of product surface. Through this structure, scientists also can increase the light efficiency. Planar is a complicated and precise technique created to control this structure. Light pass through the secondary active layer, this structure can improve the light efficiency to 80%. However, it is in the case of reducing internal quantum efficiency. In order to address this problem, scientists installed Resonant Cavity on photonic crystal LEDs. This design was named as Resonant Cavity LED. Among these LEDs, scientists configured photonic crystals. This method can increase the light efficiency to around 60%.
Because of the diffraction, Photonic Crystal Blue-ray LED can revise the light angle. Some technical processes should be taken to convince that the revised light angle be smaller than the critical angle of used media. Restricted by the critical angle, normally only 4% light can be emitted. Relatively Photonic Crystal Blue-ray LED with active layer has a much wider emitting angle, having wider area to send out rays, can consequently have higher light efficiency.