Tailoring the Luminescent Properties of SrS:Ce3+ by Sr-Deficiency and Na+ Doping

Ce3+-doped SrS phosphors with a charge-compensating Na+ addition were successfully synthesized via a solid-state reaction method, and the related X-ray diffraction patterns can be indexed to the rock-salt-like crystal structure of the Fm (3) over barm space group. SrS:(Ce3+)(x) (0.005 <= x <= 0.05) and SrS:(Ce3+)(0.01),(Na+)(y) (0.005 <= y <= 0.030) phosphors were excited by 430 nm UV-Vis light, targeted to the 5d(1) -> 4f(1) transition of Ce3+. The composition-optimized SrS:(Ce3+)(0.01), (Na+)(0.015) phosphors showed an intense broad emission band at lambda = 430-700 nm. The doping of Na+ was probed by solid-state nuclear magnetic resonance. The 430 nm pumped white light-emitting diode structure fabricated with a combination of SrS:(Ce3+)(0.01), (Na+)(0.015) and Sr2Si5N8:Eu2+ phosphors shows a color-rendering index (R-a) of 89.7. The proposed strategy provides new avenues for the design and realization of novel high color quality solid-state LEDs.