Reddish-Orange emitting thermally stable Sm3+ doped Sr2LaSbO6 phosphor for applications in w-LEDs

Abstract

A series of Sm³⁺ ions activated Sr₂LaSbO₆ phosphors was synthesised using the traditional solid-state reaction (SSR) method. This work presents Sr₂LaSbO₆ as a novel host material, in contrast to previously examined Sm³⁺-doped phosphors. It uses its double perovskite structure and LaO₆ octahedral coordination to improve light efficiency and stability, an aspect not fully investigated in perovskite-based phosphors. The phase purity of the synthesized materials was inspected using X-ray diffraction (XRD) characterization technique. The luminescent properties were analysed by photoluminescence emission and excitation (PL) spectra, temperature dependent PL (TD-PL) and decay curves. The XRD results matched the standard JCPDS suggesting that the prepared samples comprise of a pure cubic phase structure. When subjected to 407 nm excitation, the phosphors exhibit intensity peaks at 612 nm corresponding to the transition ⁶G_5/2 → ⁵H_7/2. The PL intensity of the samples increased with the increasing concentration of Sm³⁺ ions until concentration quenching occurred at x = 3.0 mol%. The stability and activation energy of the phosphor was calculated with the help of temperature dependant photoluminescence and the phosphor was found out to be highly stable at high temperatures. Most white LEDs use a blue LED chip coated with a yellow phosphor (typically YAG:Ce – Yttrium Aluminium Garnet doped with Cerium). This YAG:Ce phosphor converts some of the blue light into longer wavelengths, producing a broad-spectrum white light. However, this method tends to be weaker in the deep red part of the spectrum, making the light appear cooler and sometimes slightly bluish resulting in high CCT and low CRI. In order to address the prevalent problem of weak red component in white LEDs, which frequently results in low colour rendering index (CRI), this study proposes a Sm³⁺-doped Sr₂LaSbO₆ phosphor with high reddish-orange emission. With its efficient 406 nm excitation, the phosphor complements commercial near-UV/blue LEDs and is hence ideal for real-world LED applications. With an activation energy of ΔE = 0.424 eV, it has a strong luminous thermal stability that outperforms several previously reported phosphors, guaranteeing better performance in high-temperature lighting and display technologies. Furthermore, the material has excellent colour purity (96%), putting its emission in the warm red–orange region, which is essential for producing high-quality white light in plasma display panels (PDPs) and solid-state lighting (SSL). These properties make this phosphor a highly efficient red-emitting component, significantly improving the color rendering and performance of w-LEDs.