There are three kinds of technology to make the white LED currently. One kind is to produce white light by mixing with various colors, its principle is based on three basic color in the chromaticity. The specific method is to place red, green, blue LED very close to, control their output ratio, by mixing white is coming. The second method is to coat the fluorescent powder outside blue LED. Specific process is to coat earth garnet series fluorescent at the emission peak 450~470nm wavelength range Blu-ray LED Surface, the phosphor emits yellow light in the blue light irradiation, so that part of the blue light turns into a yellow light and the remaining blue mixture can form a white LED.
Because the rare earth garnet fluorescent powder has two characteristics, firstly its emission pea is in the range of 500~580nm, i.e. any position for yellow light region, secondly,its best excitation wavelength is in the range of 430~480nm, so that the series of fluorescent powder, added with different wavelength of blue light LED, can produce different color temperature white LED . At the same time, another method to product white led by coating blue LED chip with fluorescent powder in the following way to implement, i.e.Using blue LED to excite green and red fluorescent powder, in which green fluorescent powder can be the rare earth garnet fluorescent powder at emission peak of 500~530nm, while the red fluorescent powder of high enough luminous efficiency material not found, usually with europium oxide or manganese activated, or salts, also may be organic light-emitting materials by europium activating, the situation after Improving fluorescent powder in the red part increases significantly The third kind method of making white LED , method of products, due to Purple Light or UV LED, which provides a violet or purple, external Light excite three primary colors fluorescent powder or a variety of light color fluorescent, resulting in white way.
Because of the violet light, especially UV energy higher than blue, the prepared white LED, light efficiency can be further improved, and its wider spectral range, color rendering index can be further increased, and according to the needs ,different color or different color LED products can prepared.