Stable and efficient narrow-band red emitters with high colour purity for white LEDs and plant growth applications

Abstract

The search for extremely narrow-band new red emitters is essential for smart displays and lighting applications. Herein, we report the synthesis of a series of red-emitting Eu³⁺-substituted Li₃BaSrY₃(WO₄)₈ and solid-solution (Li₃BaSrY_0.3Eu_2.7(WO₄)_8−y(MoO₄)_y) phosphors with a stratified scheelite structure and the systematic investigation of their optical properties. All the compositions show broad absorption (charge transfer (O²⁻ → M⁶⁺)) extended up to the blue region along with strong characteristic Eu³⁺ excitation lines. The phosphor compositions exhibit proficient narrow-band red emission (quantum yield up to 85%; full width at half maximum (FWHM) = 6 nm; CIE colour coordinates x = 0.65, y = 0.35, i.e. approaching the NTSC standard for red colour) of exceptional colour purity (94% to 98%), and this host supports heavy trivalent Eu activation (showing zero concentration quenching of the emission (Eu-rich lattice)). The dominating electric dipole (⁵D₀ → ⁷F₂, red emission) transition shows Eu³⁺-ion occupancy in the non-centrosymmetric site in the host lattice. The selected composition shows better absolute quantum efficiencies compared to commercial phosphors. The presently synthesized phosphors have proven to be thermally stable against the temperature quenching effect. The fabricated red LED showed excellent performance, colour purity, LER and CIE values. The excellent optical properties, quantum yield and thermal stability make the phosphor applicable as a red component in solid-state lighting devices and as a light source for plant growth applications.