Design of a mixed-anionic-ligand system for a blue-light-excited orange-yellow emission phosphor Ba1.31Sr3.69(BO3)3Cl:Eu2+

Abstract

The essence of improving the quality of white-light-emitting diodes (w-LEDs) is to explore effective red-emitting phosphor materials. It is well known that the redshifts of excitation and emission spectra are related to crystal field splitting (ε_cfs), centroid shift (ε_c) and Stokes shift (ΔS). In this article, the design of a system of mixed-anionic-ligands with different electronegativity and ion radius is introduced to achieve the redshift of excitation and emission spectra, which can not only effectively improve ε_cfs, but also has a positive impact on the increase of ε_c and ΔS. Ba_1.31Sr_3.69(BO₃)₃Cl:Eu²⁺ emerged as a new high-performance orange-yellow-emitting phosphor, which can efficiently be excited by a blue InGaN chip and exhibit a broad asymmetric band covering from 480 to 750 nm with a peak centered at 595 nm. Based on density functional theory calculations from first principles, the orange-yellow emission is caused by the Eu 4f electronic structure. Compared with commercially available w-LED phosphor Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺), the more red-emitting component in this phosphor leads to an excellent color rendering index (CRI, R_a = 91) and a lower correlated color temperature (CCT, 4568 K) when employed in a phosphor-converted LED (pc-LED). In addition, good resistance to thermal quenching is also shown in this material; its integrated intensity at 373 K still maintains ∼86.4% of the one at room temperature. These results indicate that the Ba_1.31Sr_3.69(BO₃)₃Cl:Eu²⁺ phosphor can be a promising candidate for high quality white pc-LEDs.