Energy transfer mechanisms and color-tunable luminescence of Tm3+/Tb3+/Eu3+ co-doped Sr4Nb2O9 phosphors for high-quality white light-emitting diodes

Abstract

This paper investigates the synthesis and luminescence characteristics of Tm³⁺/Tb³⁺/Eu³⁺ co-doped Sr₄Nb₂O₉ (SNB) phosphors as potential candidates for white light-emitting diodes (WLEDs). The study explores the energy transfer mechanisms and color-tunable characteristics of these phosphors. The SNB phosphors were prepared using a solid-state reaction method, and their structural and morphological properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FT-IR) spectroscopy. The diffuse reflectance, photoluminescence (PL) and time resolved photoluminescence (TRPL) properties were investigated, revealing efficient energy transfer processes from Tm³⁺ to Tb³⁺ and Eu³⁺ ions. The energy transfer mechanisms were determined through critical distance calculations and analysis of multipolar interactions. The co-doped phosphors exhibited tunable emission colors ranging from blue to white light, with controllable correlated color temperatures (CCTs) and high color rendering indices (CRIs). The CIE chromaticity coordinates were optimized to approach neutral white light. The PL intensity is maintained at 81.19% at 150 °C of that of room temperature which showcases the remarkable thermal stability of the as-prepared phosphors. The results highlight the potential of Tm³⁺/Tb³⁺/Eu³⁺ co-doped SNB phosphors for generating high-quality, color-tunable white light for advanced lighting applications.