A green-yellow emitting oxyfluoride solid solution phosphor Sr2Ba(AlO4F)1−x(SiO5)x:Ce3+ for thermally stable, high color rendition solid state white lighting

Abstract

A near-UV excited, oxyfluoride phosphor solid solution Sr_1.975Ce_0.025Ba(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 Ce³⁺ 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.