Nitride-based red-emitting phosphors in RGB (red-green-blue) lighting systems
Embodiments of the present invention are directed to nitride-based, red-emitting phosphors in red, green, and blue (RGB) lighting systems, which in turn may be used in backlighting displays and warm white-light applications. In particular embodiments, the red-emitting phosphor is based on CaAlSiN 3 type compounds activated with divalent europium. In one embodiment, the nitride-based, red emitting compound contains a solid solution of calcium and strontium compounds (Ca,Sr)AlSiN 3 :Eu 2+ , wherein the impurity oxygen content is less than about 2 percent by weight. In another embodiment, the (Ca,Sr)AlSiN 3 :Eu 2+ compounds further contains a halogen in an amount ranging from about zero to about 2 atomic percent, where the halogen may be fluorine (F), chlorine (Cl), or any combination thereof. In one embodiment at least half of the halogen is distributed on 2-fold coordinated nitrogen (N2) sites relative to 3-fold coordinated nitrogen (N3) sites.
1. A nitride-based, red emitting compound having the formula MAlSiN 3 :Eu 2+ , wherein M is at least one of Ca and Sr, further comprising a halogen whose content ranges from greater than about zero to about 2 atomic percent, wherein at least half of the halogen is distributed on 2-fold coordinated nitrogen (N2) sites relative to 3-fold coordinated nitrogen (N3) sites.
2. The compound of claim 1 , wherein the halogen is selected from the group consisting of F and Cl.
3. The compound of claim 1 , wherein the impurity oxygen content is less than about 2 percent by weight.
4. The compound of claim 1 , wherein the impurity oxygen content is less than about 1.9 percent by weight.
5. The compound of claim 1 , wherein the impurity oxygen content is less than about 1.8 percent by weight.
6. The compound of claim 1 , wherein the halogen is F.
7. The compound of claim 1 , wherein M consists of Ca and Sr.
8. An RGB lighting system for use in a white LED or backlighting display application, the RGB lighting system comprising:
the nitride-based, red-emitting phosphor according to claim 1 ,
a green phosphor, and
a blue LED emitting in a wavelength ranging from about 400 nm to about 550 nm.
9. The compound of claim 1 , wherein at least 80% of the halogen is distributed on 2-fold coordinated nitrogen (N2) sites relative to 3-fold coordinated nitrogen (N3) sites.
10. The compound of claim 9 , wherein the impurity oxygen content is less than about 2 percent by weight.
11. The compound of claim 9 , wherein the impurity oxygen content is less than about 1.9 percent by weight.
12. The compound of claim 9 , wherein the impurity oxygen content is less than about 1.8 percent by weight.
13. The compound of claim 9 , wherein the halogen is selected from the group consisting of F and Cl.
14. The compound of claim 9 , wherein the halogen is F.
15. The compound of claim 9 , wherein M consists of Ca and Sr.
16. An RGB lighting system for use in a white LED or backlighting display application, the RGB lighting system comprising:
the nitride-based, red-emitting phosphor according to claim 9 ,
a green phosphor, and
a blue LED emitting in a wavelength ranging from about 400 nm to about 550 nm.