Highly efficient green-emitting phosphor Sr4Al14O25:Ce,Tb with low thermal quenching and wide color gamut upon UV-light excitation for backlighting display applications

Abstract

Highly efficient and stable inorganic phosphors with high response to near-ultraviolet excitation are essential to the performance enhancement of phosphor converted backlighting devices. Herein, highly efficient green-emitting phosphors Sr₄Al₁₄O₂₅:Ce,Tb (SAO:Ce³⁺,Tb³⁺) with a main narrow emission band at 544 nm originated from Tb³⁺ and a broad excitation band in the 250–400 nm region thanks to the sensitization of Ce³⁺ are obtained using a high temperature solid-state reaction method. The photoluminescence quantum yield is as high as 47.04% and the full width at half maximum is as small as ∼10 nm under the excitation of 348 nm n-UV light. The dipole–dipole interaction dominates the Ce³⁺ → Tb³⁺ energy transfer process and the energy transfer efficiency can reach 85% or even higher. The emission intensity @423 K for the SAO:Ce³⁺,Tb³⁺ samples remains no less than 80% of that at room temperature and the thermal quenching temperature exceeds 523 K, indicating an excellent thermal stability. Prototype WLEDs fabricated by combining the blue BaMgAl₁₀O₁₇:Eu²⁺, green SAO:Ce³⁺,Tb³⁺ and red K₂SiF₆:Mn⁴⁺ phosphors with a 350 nm n-UV LED chip show a color gamut of 85.34% National Television System Committee (NTSC) standard, which is better than that of some other existing green phosphors. This work demonstrates that the management of energy-transfer efficiency from Ce³⁺ to Tb³⁺ ions in perfectly matched inorganic compounds provides a useful and effective approach to design new green phosphors with ultra-narrow emission bands for backlit displays.