Theoretically Guided Development of Excitation-Wavelength-Dependent Multifunctional Phosphor Based on Gallium Vacancy Perturbation

Constructing multifunctional phosphors grounded in the intricate relationship between energy level structures and luminescent properties has captivated researchers in the luminescent material field. Herein, using the embedded cluster multiconfigurational ab initio method, the energy levels of Bi³⁺ in the SrLaGa₃O₇ host at different geometries were calculated, which results in the establishment of complete configurational coordinate curves, yielding breathing mode vibrational frequencies and equilibrium bond lengths for all excited states. These curves supply deep insight into the luminescence properties of Bi³⁺-doped phosphors and highlight the impact of ions in the second coordination sphere on luminescence. Inspired by the calculated results, we designed SrLaGa_3(1–x)O_7−δ:0.01 Bi³⁺ phosphors with different Ga³⁺ reductions. The artificially introduced gallium vacancy results in perturbed Bi³⁺ luminescence, as verified by systematic experimental analysis, and causes the material to exhibit a novel greenish-yellow emission band in addition to the original blue band, leading to excitation-wavelength-dependent multicolor emission phosphors. The obtained phosphor displayed a multicolor fluorescent anticounterfeiting function, and a multicolor switching system was designed with the merits of direct visualization and easy identification of encrypted information. Additionally, white light-emitting diodes were fabricated by employing the prepared phosphors and UV chips. These results indicate that the SrLaGa_3(1-x)O_7-δ:0.01 Bi³⁺ phosphor has significant potential in both anticounterfeiting and lighting applications. Our study demonstrates the necessity of considering two coordinate spheres of ligands when interpreting the luminescent properties and illustrates the effectiveness of spectral design under theoretical guidance, providing a feasible path for the development of multifunctional phosphors.