A green-yellow emitting oxyfluoride solid solution phosphor Sr2Ba(AlO4F)_(1-x)(SiO5)_x:Ce~(3+) for thermally stable, high color rendition solid state white lighting

摘要

A near-UV excited, oxyfluoride phosphor solid solution Sr_(1.975)Ce_(0.025)Ba(AlO4F)_(1-x)(SiO5)_x has been developed for solid state white lighting applications. An examination of the host lattice, and the local structure around the Ce~(3+) activator ions through a combination of density functional theory, synchrotron X-ray and neutron powder diffraction and total scattering, and electron paramagnetic resonance, points to how chemical substitutions play a crucial role in tuning the optical properties of the phosphor. The maximum emission wavelength can be tuned from green (λ_(em) = 523 nm) to yellow (λ_(em) = 552 nm) by tuning the composition, x. Photoluminescent quantum yield is determined to be 70 ± 5% for some of the examples in the series. Excellent thermal properties were found for the x = 0.5 sample, with the photoluminescence intensity at 160 °C only decreased to 82% of its room temperature value. Phosphor-converted LED devices fabricated using an InGaN LED (λ_(max) = 400 nm) exhibit high color rendering white light with R_a = 70 and a correlated color temperature near 7000 K. The value of R_a could be raised to 90 by the addition of a red component, and the correlated color temperature lowered to near 4000 K.