Effect of phosphor on LED package

[Source: "High-tech LED-technology and application" January issue Zhao Kun / Zhang Hao]

First, the impact of particle morphology

In an LED package, the brightness of the phosphor directly affects the luminous flux of the product. The brightness of the phosphor is mainly determined by its chemical composition, crystal structure and particle morphology. For the same type of phosphor, the crystals are well crystallized and the regularity of the particle morphology is usually higher.

At present, most of the phosphor manufacturers use high-temperature solid-phase method to synthesize phosphors. Compared with other synthetic methods, the phosphors synthesized by this method have good crystals, high brightness and easy mass production. However, the use of this method to synthesize phosphors also has drawbacks, mainly in the sintering process, which tends to cause sintering phenomenon, which causes the phosphors to be dispersed in the process, and the grinding often causes damage to the phosphor crystals and causes a decrease in brightness. . At the same time, since the specific surface area of ​​the fine particles and the irregular particles in the phosphor is relatively large, these phosphor particles are more susceptible to erosion during the operation of the LED, resulting in a decrease in brightness.

Fig.1 SEM image of different particle morphology phosphors

Figure 1 is an SEM image of phosphors with different particle topography. Table 1 shows the initial luminous flux and light decay data of LED devices packaged with phosphors of different particle morphology. The packaging, test conditions and materials other than phosphor are the same. It can be seen from Fig. 1 and Table 1 that the good shape of the phosphor particles directly affects the initial luminous flux and light decay of the packaged LED device. The better the morphology of the phosphor particles, the smaller the light attenuation of the LED device after encapsulation. This rule applies not only to the aluminate yellow phosphor but also to other types of phosphors.

For more information, please refer to the January issue of "High-tech LED-Technology and Applications" magazine.

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