Highly efficient blue-emitting silicate phosphor BaY4Si5O17:Eu2+ with superior thermal stability for full-visible-spectrum white LEDs

Abstract

Activators that occupy a single lattice site with high structural rigidity in the host can endow the phosphor with a superior thermal stability and high quantum yield. The monoclinic structure phosphor BaY₄Si₅O₁₇:Eu²⁺ (BYSO: Eu²⁺) features a single BaO₈ site within the host lattice for the occupation of the Eu²⁺ ion, offering a broad n-UV excitation bandwidth ranging from 250 to 400 nm and a blue emission band peaking at 464 nm. This phosphor exhibits remarkably low thermal quenching, with integrated emission intensities at 373 K and 423 K maintaining 87 % and 76.9 % of their values at 298 K, respectively. The component substitution strategy of Sr²⁺ replacing Ba²⁺ has been found to enhance thermal stability, retaining over 87 % of its initial luminescence intensity at 423 K and displaying a high thermal activation energy of 0.14 eV, which effectively reduces thermally induced non-radiative energy transfer. Moreover, this substitution improves luminescence efficiency, with the quantum yield increasing from 77.84 % to 84.43 %. A white light-emitting diode was constructed using this phosphor in conjunction with commercial phosphors on a 360 nm UV-emitting chip, resulting in CIE color coordinates of (0.3343, 0.3528), a color rendering index (CRI) of 94.5, and a color temperature (CCT) of 5431 K at a current of 140 mA. The outstanding properties of BYSO: Eu²⁺ indicate their suitability for applications in high-color-quality full-visible-spectrum LED lighting.