Blue light‐excitable Eu‐doped yellow emitting borate KSr4B3O9 phosphor for white light‐emitting diodes

Abstract

AbstractIn the development of novel phosphors for solid‐state light applications, the suitable excitation peak matching with blue LED chip was usually neglected. However, the excitation peak of phosphors was strongly related to the Stocks shift, crystal field splitting, and centroid shift. Here, an environmentally friendly borate phosphor KSr4B3O9: Eu2+ with the maximum excitation peak position at ∼460 nm was prepared in a quite mild synthesis condition. With a blue light excitation, KSr4B3O9: Eu2+ phosphors could emit a bright yellow light centered at ∼560 nm, which could be attributed to the drastic centroid shift and strong crystal field splitting. The strong electron cloud overlaps between Eu–O and the high electron density on the O atom turned out to be the main reason that induces the strong nephelauxetic effect. In addition, the strong crystal field splitting was benefited to the relatively short average Sr–O distance and the large Sr–O distances distribution range from ∼2.23 to 2.96 Å. Meanwhile, the Eu2+ occupation of all the Sr2+ sites in KSr4B3O9 host identified by Rietveld refinement, cryogenic emission spectra, and Eu3+ fluorescent probe gave another evidence to the wide absorption region. The final WLED device and three‐dimensional colorful artwork were fabricated and displayed to suggest a potential application in the solid‐state lighting field and some expressions of esthetic concepts.