Sr-Containing Sialon Phosphor for White LEDs

Although white light-emitting diodes (LEDs) composed of a blue LED and a yellow-emitting phosphor have been widely used in recent years, they have insufficient color rendering due to a lack of red spectral emission. To realize a warm-white LED with higher color rendering, a redemitting phosphor that can be excited by blue LED light is required.

Toshiba has developed a red-emitting phosphor that has a new host material, Sr-containing sialon (Sr₂Si₇Al₃ON₁₃: Sr-SiAlON), doped with europium ion (Eu²⁺ ) as an activator. It achieves both high efficiency and small thermal quenching under excitation by blue light, which is essential for high-temperature operation. The wavelength of peak emission in the red emission band can be widely shifted from 580nm to 645nm by adjusting the crystal composition and the sintering conditions. Furthermore, the efficiency of this phosphor is not significantly decreased with changes in the wavelength of the blue LED or the operating temperature.

These features indicate the high potential of this red-emitting phosphor for application to white LEDs that can transform the cold-bluish-white light of conventional white LEDs into warmwhite light suitable for general lighting purposes.

Cross-sectional structure of white LED with high color rendering index (left)
Emission from red-emitting sialon phosphor (right)