INDUSTRY LEDs
Looking to the solid state lighting market, our GAL phosphor offers a broader emission spectrum than silicate phosphors, or even YAG materials, so it is particularly ideal for bulb replacement applications where a broad spectral output similar to incandescent light is required. Meanwhile, our red nitride phosphors have an emission bandwidth that is narrower, similar to those of silicates. When emitting in the red, a
narrow emission is desired – if there is spectral output at infrared wavelengths, where the eye is insensitive, the energy is wasted on unseen light.
Both our red and green phosphors have the edge over earlier silicates in terms of performance in mid to high power LEDs. In a high power LED, the phosphor typically reaches a temperature of 100 °C or higher, and in that regime the GAL and red nitride phosphors can deliver
an efficiency that is 10-15 percent higher than that of silicates. This greater thermal stability is highlighted by measurements showing that the emission intensity of GAL phosphors declines by just a few percent between 0 °C and 200 °C, compared to a fall of more than 20 percent for traditional YAG (see Figures 3 and 4).
What’s more, the combination of our GAL and red phosphors can enable a near- perfect colour rendering of up to 98 CRI.
Figures 3: Green aluminate (GAL) has excellent thermal stability, allowing it to aid the production of efficient LED light bulbs operating at high current densities.
Figure 2: Today, three different methods are used to make a white-emitting LED product. These variations are associated with the phosphors, which are directly applied to the LED chip. The pioneers of the white-emitting LED added a yellow phosphor to a blue LED (a). Higher colour-quality, which comes at the expense of inferior efficiency, is possible by adding a red phosphor (b), or employing the combination of a red and a green phosphor (c).
Figure 4: Intematix has improved thermal stability by turning to new materials. 46
www.compoundsemiconductor.net June 2014
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