White afterglow achieved in Eu2+, Ce3+, Dy3+co-doped LiSr4(BO3)3 phosphor

Abstract

In prior study by our team, orange-yellow afterglow was observed in Eu²⁺ and Dy³⁺ co-doped LiSr₄(BO₃ )₃ phosphor due to the emission from Eu²⁺ center. In this study, further incorporation of Ce³⁺into the phosphor lead to the observation of white afterglow due to the mixed result of blue light from Ce³⁺ and orange-yellow light from Eu²⁺ centers. Upon ultraviolet excitation, the phosphor displays a spectrum characterized from blue emission of Ce³⁺ at 462nm and orange-yellow emission of Eu²⁺ at 632nm. Fine-tuning the concentration of Ce³⁺ enabled the realization of white luminescence in LiSr₄(BO₃)₃: Eu²⁺, Ce³⁺ and Dy³⁺phosphor with chromaticity coordinates of (0.3979, 0.2939). The photoluminescence intensities of the samples could be modulated by incorporating varying amounts of Ce³⁺ ions, with a critical quenching concentration identified with 0.16 Ce³⁺. White afterglow is also observed after the removal of the light illumination due to the existence of suitable electron traps with optimal trap depth created by the co-doped Dy³⁺. The underlying mechanism proposes that the white afterglow is generated by the mixed lights of blue and orange-yellow that are created by the recombination of heat-released electrons from the trap centers with pre-existing holes in the Ce and Eu emission sites.