Spectral investigations of dysprosium (Dy3+) ions doped ZnBiNaPSr oxyfluoride glasses for intense white light emitting diodes (w-LEDs)

Abstract Oxyfluoride (P2O5 + Bi2O3 + Na2CO3 + SrCO3 + ZnF2) glasses doped with different dysprosium (Dy3+) ion concentrations (0.5, 1.0, 1.5 & 2 mol %) have been synthesized using conventional melt quenching technique. The Physical and optical parameters such as density (ρ), refractive index (n), polaron radius (rp), interionic distance (ri), field strength (F), electron polarizability (αe), molar refractivity (RM), reflection loss (R), etc., were evaluated. The X-ray diffractograms were recorded in the 10–900 region, showed amorphous nature. Surface morphological studies were performed with SEM and elemental analysis has also been performed with EDS. The absorption spectra consist of a few well-defined high intense bands in the UV–Vis-NIR region. The optical band gaps were estimated from the tauc’s plots drawn from the absorption spectra and obtained values exhibited nonlinear behaviour with dopant ion concentration. The emission spectra were recorded by monitoring the excitation wavelength at 453 nm which consists of three emission bands at 487, 557 and 667 nm, due to f-f characteristic transitions of Dy3+ ion. The Judd-Ofelt and radiative parameters have been calculated from absorption and luminescence spectra. It has been noticed that the concentration quenching effect was observed for higher concentrations (1.5 and 2.0 mol %) in the present glass series. The emission intensity ratio between yellow and blue color bands and CIE color coordinates were evaluated. The correlated color temperature (CCT) and color purity (CP) has been evaluated using CIE 1931 chromaticity diagram. The ZnBiNaPSr: Dy1.0 glass exhibits superior luminescent properties than other concentrations and it was found to be the most prominent device for white light applications.