Multiple Energy Transfer in Luminescence-Tunable Single-Phased Phosphor NaGdTiO₄: Tm³⁺, Dy³⁺, Sm³

Advances in solid-state white-light-emitting diodes (WLEDs) necessitate the urgent development of highly efficient single-phase phosphors with tunable photoluminescence properties. Herein, the Tm³⁺, Dy³⁺, and Sm³⁺ ions are incorporated into the orthorhombic NaGdTiO₄ (NGT) phosphors, resulting in phosphors that fulfill the aforementioned requirement. The emission spectrum of Tm³⁺ ions overlaps well with the adsorption spectra of both Dy³⁺ and Sm³⁺ ions. Under the excitation at 358 nm, the single-phase NaGdTiO₄: Tm³⁺, Dy³⁺, Sm³⁺ phosphor exhibits tunable emission peaks in the blue, yellow, and red regions simultaneously, resulting in an intense white-light emission. The coexisting energy transfer behaviors from Tm³⁺ to Dy³⁺ and Sm³⁺ ions and the energy transfer from Dy³⁺ to Sm³⁺ ions are demonstrated to be responsible for this phenomenon. The phosphors with multiple energy transfers enable the development of single-phase white-light-emitting phosphors for phosphor-converted WLEDs.