Extra-Broad Band Orange-Emitting Ce³⁺-Doped Y₃Si₅N₉O Phosphor for Solid-State Lighting: Electronic, Crystal Structures and Luminescence Properties

Luminescent materials play an important role in making solid state white light-emitting diodes (w-LEDs) more affordable home lighting applications. To realize the next generation of solid-state w-LEDs with high color-rendering index (CRI), the discovery of broad band and long emission wavelength luminescent materials is an urgent mission. Regarding this, the oxonitridosilicate Y 3 Si 5 N 9 O with a high nitrogen concentration should be a suitable host material to achieve those promising luminescent properties. In this work, a phase-pure Ce 3+ -doped Y 3 Si 5 N 9 O was successfully synthesized through the carbothermal reduction and nitridation method. Y 3 Si 5 N 9 O:Ce 3+ shows an emission maximum at 620 nm and an extremely broad emission band with a full-width at half-maximum (fwhm) of 178 nm. The electronic and crystal structure calculations indicate an indirect band gap of 2.6 eV (experimental value: 4.0 eV), and identify two Ce 3+ sites with different local environments that determine the luminescence properties. The orange-emitting phosphor has the absorption, internal and external quantum efficiencies of 89.5, 17.2, and 15.6% under 450 nm excitation, respectively. The valence state of Ce, cathodoluminescence, decay time, and thermal quenching of the phosphor were also investigated to understand the structure–property relationships.