Spectroscopic properties of Dy3+-doped oxyfluoride glasses for white light emitting diodes

Dy3+-doped oxyfluoride (NbFSDy: SiO2-Nb2O5-K2O-ZnF2-LiF-Dy2O3) glasses were prepared by melt-quenching technique and their spectroscopic properties have been investigated. Glass transition and crystallization temperatures have been determined. Phonon energy and vibrational groups of the host matrix have been analyzed from the Raman spectrum. Judd-Ofelt analysis has been carried out to obtain intensity parameters which are used to predict radiative properties for the 1.0 mol% of Dy2O3 doped glass. The characteristic emission parameters such as effective bandwidth and the stimulated emission cross-section have also been intended from the emission spectra for the F-4(9/2) level of Dy3+ ions. Sharp emission peaks were observed at 485 nm (blue) of F-4(9/2) --> H-6(15/2) and 577 nm (yellow) of F-4(5/2) --> H-6(13/2) transitions under different pump wavelengths. The CIE co-ordinates for an optimal concentration (0.1 mol% of Dy2O3) were fallen in the white light region for all the pump wavelengths. The correlated color temperature decreases from 5593 K (closer to the day light value of 5500 K) to 5003 K with increase in pump wavelengths. These results indicate that 0.1 mol% Dy2O3-doped glass can be considered for the development of white light emitting diodes.