Tuning of emission in BaLa1−x−yGa3O7:xDy3+, yEu3+ by local symmetry effects for WLEDs

Abstract

Melilite structured phosphor is a significant luminescent material, but limited by its structure and luminescent properties, its luminescence intensity and spectral composition cannot satisfy the application requirements. To solve this issue, we look into the connection for the first time between the amount of rare-earth elements added and the symmetry of structure in melilite phosphors. We got the results by looking at the PL spectral data and J-O parameters of the melilite phosphor BaLa1−x−yGa3O7:xDy3+,yEu3+. Dy3+ was located in the low symmetry site, resulting in the local asymmetry being successfully enhanced to obtain warm-white color coordinates (0.398, 0.393) by adjusting the concentration of Eu3+ to vary the Y/B ratio of Dy3+ and the R/O ratio of Eu3+. Meanwhile, in the way that energy is transferred with an electric quadrupole-electric quadrupole between phosphor dopant ions. The energy transfer efficiency of Dy3+-Eu3+ is up to 81.99 %. At 475 K, the phosphor maintains an intensity of 81.1 % and exhibits reliable thermal stability. The color purity and EQE of BLGO:0.40Eu3+ are 49.7 % and 38.56 %, respectively. These results reveal that modifying the local symmetry surrounding the doped ions allows for adjusting the luminescence's wavelength composition. This approach can be applied to phosphors generated for warm white light-emitting diodes (WLEDs) with a single matrix.