First of all, even without using phosphors, colored LEDs of different colors such as red, yellow, green, blue, and purple can be prepared. However, because the luminous efficiency of these different color LEDs is very different, fluorescent After the powder is produced, the advantages of high luminous efficiency of LEDs in certain bands can be used to prepare LEDs in other bands to improve the luminous efficiency of this band. For example, some green-band LEDs have low efficiency. Taiwanese manufacturers use the phosphors we provide to prepare a higher-efficiency LED called "Apple Green" for mobile phones. Among them, white light sources are undoubtedly the most in demand. , so LED phosphors are the most widely used in the field of white light emission. There are many ways to achieve white light in LEDs, and the earlier developed and industrialized method is to coat the LED chip with phosphor to achieve white light emission.
There are three main methods for using phosphors to achieve white light in LEDs, but they are not fully mature, which seriously affects the application of white LEDs in the lighting field.
The first method: blue LED chip yellow phosphor. This technology is monopolized by the Japanese company Nichia, and a principle disadvantage of this solution is that the emission spectrum of Ce3 ions in the phosphor does not have a continuous spectrum. Characteristics and poor color rendering make it difficult to meet the requirements of low color temperature lighting. At the same time, the luminous efficiency is not high enough and needs to be improved by developing new high-efficiency phosphors.
The second method: blue LED green phosphor pink red phosphor, the blue light emitted by the chip and the green light and red light emitted by the phosphor are combined to obtain white light, with better color rendering. However, the effective conversion efficiency of the phosphors used in this method is low, especially the efficiency of red phosphors needs to be greatly improved.
The third method: Purple LED three-primary color phosphors (phosphors of multiple colors), using the long-wave ultraviolet light (370nm-380nm) or violet light (380nm-410nm) emitted by the chip to stimulate fluorescence To achieve white light emission, this method has better color rendering, but it also has problems similar to the second method, and the current red and green phosphors with higher conversion efficiency are mostly sulfide systems, which have stable luminescence. Due to poor performance and large light attenuation, it has become an urgent task to develop high-efficiency, low light attenuation phosphors for white LEDs.
2. Use the advantages of high luminous efficiency of LEDs in a certain band to prepare LEDs in other bands
Although phosphors are not used, red, yellow, green, blue, purple, etc. can be produced. However, since the luminous efficiency of these different color LEDs is very different, after using phosphors, the advantages of high luminous efficiency of LEDs in certain bands can be used to prepare LEDs in other bands to improve the luminous efficiency of this band. For example, some green-band LEDs have low efficiency. Taiwanese manufacturers used the phosphors we provided to prepare a higher-efficiency LED called "Apple Green" for mobile phone backlights, and achieved good economic benefits.
3. Make the LED light color softer and brighter
Although the most widely used LED is still in the field of white light, due to its special advantages, after using phosphors, some The light color of LED will become softer or brighter to adapt to different application needs. It can also be used in color LEDs to a certain extent. However, the application of phosphors in color LEDs has just started and requires further in-depth research and development. development.
4. Reuse LEDs with errors in their luminous wavelength
It is still difficult to precisely control the luminous wavelength of LEDs, which will result in LEDs of some wavelengths not being used and causing waste. For example, when you need to prepare 470nm LEDs, you may prepare LEDs with a wide range from 455nm to 480nm. LEDs with emission wavelengths at both ends can only be disposed of or discarded at a cheaper price, and using phosphors can make these so-called The "waste" is transformed into the colors we need and utilized.