Structural, optical and luminescent properties of Tm3+-doped phosphate oxyfluoride glasses for blue emission solid state devices

Abstract

In this work, the visible luminescence of P2O5-KF-Al2O3 glasses with Tm2O3 was studied. The Tm3+ ion can have a strong blue emission, which allows the development of LEDs in this color region. This study refers to the synthesis of oxyfluorophosphate glasses, 38P2O5+(50-x)KF+12Al2O3+xTm2O3 (PKAl:Tm), with x = 0.25, 0.50, 0.75, and 1.00 mol%, by the melt-quenching method. The prepared materials showed amorphous characteristics verified by XRD data. The absorption spectra shown six main bands characteristic of Tm3+ ions, from ground state 3H6 to excited levels 3F4, 3H4, 3H5, 3F3,2, 1G4 and 1D2, in which the intensities increased with the concentration of Tm2O3. In the FTIR spectra, it was verified that the profiles of the PKAl samples are similar to glasses based on phosphate systems. The Judd-Ofelt parameters were calculated, where for PKAl glasses the trend was Ω2>Ω4>Ω6. The excitation spectra of PKAl:Tm glasses shown an intense band centered at 358 nm (3H6→1D2). The luminescence spectra with excitation at 358 nm shown two bands at 453 nm (1D2→3F4), and 480 nm (1G4→3H6); the highest emission intensity was observed to the sample doped with 0.75 mol% of Tm2O3. The calculated CIE diagram shown that the doped samples have coordinates close to the primary blue color, which favors the application for the development of blue LEDs and wLEDs. The decay curves for the 1D2 level were fitted by single exponential with lifetime values decreasing with increasing concentration of Tm2O3. These results show that the PKAl:Tm glasses are potential candidates for applications in LEDs.