A green-yellow emitting oxyfluoride solid solution phosphor Sr ₂Ba(AlO ₄F) _1-x(SiO ₅) _x:Ce ³⁺ for thermally stable, high color rendition solid state white lighting

A near-UV excited, oxyfluoride phosphor solid solution Sr _1.975Ce _0.025Ba(AlO ₄F) _1-x(SiO ₅) _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.