Design of a mixed-anionic-ligand system for a blue-light-excited orange-yellow emission phosphor Ba1.31Sr3.69(BO3)3Cl:Eu2+†
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 (εcfs), centroid shift (εc) 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 εcfs, but also has a positive impact on the increase of εc and ΔS. Ba1.31Sr3.69(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, Ra = 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 Ba1.31Sr3.69(BO3)3Cl:Eu2+ phosphor can be a promising candidate for high quality white pc-LEDs.