Abstract
Abstract The luminescence properties of the blue emitting phosphor Sr0.25Ba0.75Si2O2N2:Eu2+ are extensively investigated. This oxonitridosilicate phosphor features strong 4f65d1 - 4f7 luminescence originating from the Eu2+ ion, with a narrow emission band peaking at 467 nm and a full width at half maximum of only 41 nm. Thermal quenching of the blue luminescence only sets in above 450 K, making this material an interesting candidate as LED conversion phosphor. The fast decay of the luminescence prevents the phosphor to be susceptible to saturation effects at high excitation fluxes. Furthermore it is proven to be chemically stable against moisture. The only drawback is the relatively low quantum efficiency of the synthesized powder, provisionally preventing this material to be used in applications. In addition, the phosphor features a weak yellow emission band, originating from small domains featuring a different crystal structure. It is shown that the majority of the powder grains only exhibit blue emission. Finally, the spectrum of a white LED, based on a UV pumping LED and three (oxy)nitride phosphors is simulated in order to assess the usefulness of blue phosphors in LEDs for lighting. Only a marginal improvement in terms of color quality can be achieved with a narrow banded phosphor, at the expense of a decrease in luminous efficacy and overall electrical to optical power efficiency. PACS 70 – Condensed Matter: Electronic structure, Electrical, Magnetic, and Optical Properties PACS 42.70.-a Optical materials
Highlights
Light-emitting diodes or LEDs are steadily consolidating their share in the lighting and display market
Synthesis and X-ray diffraction (XRD) For the synthesis of the blue emitting Sr0.25Ba0.75Si2O2N2:Eu2+ phosphor, Seibald et al used a dual step solid state synthesis based on the orthosilicate (Sr0.25Ba0.75)2SiO4:Eu2+ phosphor as intermediate product [19,24]
It could be confirmed that this synthesis method yields the described blue phosphor
Summary
Light-emitting diodes or LEDs are steadily consolidating their share in the lighting and display market. The first phosphor converted LEDs (pc-LEDs), based on a blue In1-xGaxN pumping diode and a yellow (typically Y3Al5O12:Ce3+ [1,2]) conversion phosphor, suffered from a low color rendering due to the lack of green and red light in the spectrum and of inherently high correlated color temperatures (CCT). This issue could to a great extend be solved by adding a red phosphor (for example Ca1-xSrxS:Eu2+ [3] or Sr2Si5N8:Eu2+ [4,5]). The second option, which will be pursued in this paper, uses a violet or near UV pumping diode in combination with an additional blue phosphor
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
