Aliovalent substitution toward reinforced structural rigidity in Ce3+-doped garnet phosphors featuring improved performance

Abstract

Highly efficient phosphors with thermal stability and color-tunable emission are required for the fabrication of phosphor-converted white light-emitting diodes (pc-WLEDs). Currently developed engineering strategies are generally successful in photoluminescence tuning but, unfortunately, suffer severe deterioration in emission intensity/efficiency and/or thermal stability. Herein, an efficient aliovalent substitution strategy toward reinforced structural rigidity is proposed and demonstrated experimentally. By incorporating Be²⁺ ion into the garnet-type Lu₂SrAl₄SiO₁₂:Ce³⁺ phosphor, the phosphor shows enhanced internal/external quantum efficiency, from 79.2%/26.7% to 84.5%/32.9%, photoluminescence tuning from green (peaking at ∼512 nm) to yellow (peaking at ∼552 nm), and zero thermal quenching, even up to 200 °C. The Be²⁺ substitution at the Al₂/Si₂ site enables stable and rigid local surroundings around the Ce³⁺ activator, which is responsible for the unprecedented performance. In addition, high-quality warm WLED devices with a luminous efficiency of 158.1 lm W⁻¹, correlated color temperature of 3858 K and high color rendering index of 81.7, are obtained by combining Lu₂SrAl₄SiO₁₂:Ce³⁺,Be²⁺ as the yellow emitter, CaAlSiN₃:Eu²⁺ as the red emitter and a blue-emitting InGaN chip. These findings highlight a new strategy for performance optimization of LED phosphors by selecting rigid covalent compounds with further reinforced structural rigidity via aliovalent substitution.