All-In-One Light-Tunable Borated Phosphors with Chemical and Luminescence Dynamical Control Resolution

Abstract

Single-composition white-emitting phosphors with superior intrinsic properties upon excitation by ultraviolet light-emitting diodes are important constituents of next-generation light sources. Borate-based phosphors, such as NaSrBO₃:Ce³⁺ and NaCaBO₃:Ce³⁺, have stronger absorptions in the near-ultraviolet region as well as better chemical/physical stability than oxides. Energy transfer effects from sensitizer to activator caused by rare-earth ions are mainly found in the obtained photoluminescence spectra and lifetime. The interactive mechanisms of multiple dopants are ambiguous in most cases. We adjust the doping concentration in NaSrBO₃:RE (RE = Ce³⁺, Tb³⁺, Mn²⁺) to study the energy transfer effects of Ce³⁺ to Tb³⁺ and Mn²⁺ by comparing the experimental data and theoretical calculation. The vacuum-ultraviolet experimental determination of the electronic energy levels for Ce³⁺ and Tb³⁺ in the borate host regarding the 4f–5d and 4f–4f configurations are described. Evaluation of the Ce³⁺/Mn²⁺ intensity ratios as a function of Mn²⁺ concentration is based on the analysis of the luminescence dynamical process and fluorescence lifetime measurements. The results closely agree with those directly obtained from the emission spectra. Density functional calculations are performed using the generalized gradient approximation plus an on-site Coulombic interaction correction scheme to investigate the forbidden mechanism of interatomic energy transfer between the NaSrBO₃:Ce³⁺ and NaSrBO₃:Eu²⁺ systems. Results indicate that the NaSrBO₃:Ce³⁺, Tb³⁺, and Mn²⁺ phosphors can be used as a novel white-emitting component of UV radiation-excited devices