Cationic composition engineering in double perovskite XLaLiTeO6:Eu3+ (X = Ba, Sr, Ca, and Mg) toward efficient and thermally stable red luminescence for domestic white-LEDs

Abstract

The domestic white-LEDs aim to reduce blue light exposure for daily lighting by taking the near-ultraviolet LED chip (λ_em = 395–405 nm) as the excitation source working with tricolor phosphors. However, achieving an efficient, thermally stable, and narrow bandwidth red phosphor is still challenging. Herein, the Eu³⁺ doped perovskite tellurates XLaLiTeO₆ (X = Ba, Sr, Ca, and Mg) are prepared to meet domestic lighting applications. Excited by 396 nm near-ultraviolet light, all the samples yielded typical Eu³⁺ red emissions with narrow peaks at ∼615 nm, guaranteeing high color purity exceeding 90%. Moreover, benefitting from the suppressed energy migration between Eu³⁺ due to structural confinement, the absorption factors can keep high values in XLaLiTeO₆:Eu³⁺. The cationic composition engineering by optimizing the alkaline earth occupation is proposed to greatly improve the luminescence properties of XLaLiTeO₆:Eu³⁺, leading to the high quantum efficiency (95.9%) and most thermally stable luminescence in MgLaLiTeO₆:Eu³⁺. The inner mechanism can be extended as a general model to modify the luminescence properties of Eu³⁺ doped phosphors. As a proof of concept,white-LEDs using MgLaLiTeO₆:Eu³⁺ as the red component produce warm white light with high color indexes, while reducing the blue light significantly.