Sr2Y8(SiO4)6O2:Bi3+/Eu3+: a single-component white-emitting phosphor via energy transfer for UV w-LEDs

Abstract

A series of Bi³⁺,Eu³⁺-doped Sr₂Y₈(SiO₄)₆O₂ (SYSO) phosphors were synthesized by the Pechini-type sol–gel route. XRD patterns, Rietveld refinement, FT-IR spectra, photoluminescence spectra (PL), fluorescence decay time, and quantum yields (QYs) were utilized to characterize the as-prepared samples. Intense blue-green emission due to the ³P₁ → ¹S₀ transition of Bi³⁺ ions is produced under UV excitation in Bi³⁺ singly doped SYSO samples. Spectral analysis illustrates that two kinds of Bi³⁺ ions are generated by occupying the two kinds of sites (4f and 6h) available for Y in SYSO, denoted as Bi³⁺(1) and Bi³⁺(2), corresponding to the two main emission bands at around 413 and 493 nm, respectively. A wide spectral overlap between Bi³⁺ emission and Eu³⁺ excitation spectra results in the energy transfer from Bi³⁺ to Eu³⁺. This has been demonstrated via the excitation spectra monitored at Bi³⁺ and Eu³⁺ emission bands, and the PL emission spectra and decay time of Bi³⁺ in SYSO:Bi³⁺,Eu³⁺ phosphors. The energy transfer mechanism is determined to be dipole–quadrupole interaction. The critical distance of energy transfer from Bi³⁺ to Eu³⁺ ions is calculated to be 12.78 Å based on the concentration quenching method, which is in good agreement with that of the spectral overlap route (10.03–13.37 Å). Moreover, the QYs, CIE chromaticity and thermal quenching properties have also been investigated. White emission color can be realized with the CIE coordinates (0.325, 0.311) and QY 52% for SYSO:0.08Bi³⁺,0.48Eu³⁺. The above results suggest that SYSO:Bi³⁺,Eu³⁺ can be a potential single-component white-emitting phosphor for UV w-LEDs.