Photoluminescence properties of Li2SrGeO4:RE3+ (RE = Ce/Tb/Dy) phosphors and enhanced luminescence through energy transfer between Ce3+ and Tb3+/Dy3+

Abstract

Li₂SrGeO₄:RE³⁺ (RE = Tb/Dy/Ce) phosphors were prepared by the conventional solid-state reaction. X-ray diffraction (XRD), photoluminescence (PL) spectra, and lifetimes were utilized to characterize samples. Under the excitation of ultraviolet (231 nm for Tb³⁺ and 351 nm for Dy³⁺), the Li₂SrGeO₄:Tb³⁺ and Li₂SrGeO₄:Dy³⁺ phosphors show their respective characteristic emissions of Tb³⁺ (⁵D₃,₄ → ⁷F_J′, J′ = 3, 4, 5, 6) and Dy³⁺ (⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2), respectively. Ce³⁺ activated Li₂SrGeO₄ phosphors exhibit broad band blue emission due to the 5d–4f transition of Ce³⁺. Co-doping Ce³⁺ into the LSG: Ce³⁺/Dy³⁺ samples enhances the luminescence intensity of Tb³⁺ and Dy³⁺ significantly under the excitation wavelength at 340 nm through energy transfer from Ce³⁺ to Tb³⁺/Dy³⁺. In addition, the energy transfer mechanism between Ce³⁺ and Tb³⁺/Dy³⁺ has been demonstrated to be a resonant type via a dipole–quadrupole interaction.