Luminescence properties and Judd–Ofelt analysis of Tb3+ doped Sr2YTaO6 double perovskite phosphors for white LED applications

Abstract

A series of Tb³⁺-doped Sr₂YTaO₆ double perovskite phosphors (SYT:Tb³⁺) were synthesized using a conventional solid-state reaction method. A strong green emission was observed in the SYT:Tb³⁺ phosphors, and the optimal doping concentration of Tb³⁺ was confirmed to be 5 mol%. The electric dipole–dipole interaction was ascribed to be the main mechanism for the luminescence concentration quenching. Analysis of the concentration-dependent fluorescence decay confirmed that the self-generated quenching model holds for the dynamic process of Tb³⁺ decays in SYT. Furthermore, the internal quantum efficiencies, non-radiative transition rates, and energy transfer rates of the ⁵D₄ level for the SYT:Tb³⁺ samples were estimated, respectively. The luminescence thermal stability of the sample was also evaluated based on the Arrhenius model. The chromaticity shift of the SYT:5 mol% Tb³⁺ phosphor was examined to be 0.013 when the sample temperature was increased from 303 to 483 K, thus indicating excellent chromaticity shifting resistance under high temperature conditions. Moreover, the Judd–Ofelt parameters were calculated from the emission spectra of SYT:Tb³⁺ to be Ω₂ = 0.29 × 10⁻²⁰, Ω₄ = 0.45 × 10⁻²⁰, and Ω₆ = 0.72 × 10⁻²⁰ cm², respectively. The fluorescence branching ratios and radiative transition rates for the ⁵D₄ level were calculated based on the obtained Judd–Ofelt parameters. Finally, a white light-emitting diode (LED) prototype was assembled using a 310 nm LED chip combined with a prepared green SYT:Tb³⁺ phosphor and two other commercial blue and red phosphors. The obtained warm white light exhibits good chromaticity coordinates (0.32, 0.32) and a high color rendering index of 96.1. Based on the above results, it can be known that the prepared SYT:Tb³⁺ phosphors have a potential application as green emitting phosphors in white LEDs.