Photoluminescence properties of Tm3+/Tb3+/Sm3+ tri-doped Na5Y9F32 single crystal with high thermal stability for white light-emitting diodes

Abstract

A novel Tm3+/Tb3+/Sm3+ tri-doped Na5Y9F32 single crystal was synthesized by a modified Bridgman method for the propose of white light emitting diodes. The fluorescence spectra of various Sm3+ ion concentrations and fixed 0.4 mol% Tm3+ and 0.5 mol% Tb3+ were measured and studied systematically excited by near-ultraviolet light of 355 nm. The Sm3+ ion concentration takes apparent effect on the relative intensity of peaks in the visible region and the color coordinate combining from these emission bands. A near pure white light emission with color coordinates (0.3295, 0.3057) and color temperature (5657 K) can be obtained when the concentrations of Tm3+, Tb3+ and Sm3+ ions are 0.4 mol%, 0.5 mol% and 0.8 mol%, respectively. Furthermore, the practical down-conversion internal quantum yield was measured by integrating spheres at about 14.39%. The tri-doped Na5Y9F32 single crystal shows a high thermal stability inferring from the temperature dependent emission in which the integrated emission intensities are reduced only by ∼3% with the increase of temperature from 280 to 450 K. The present results demonstrate that the Tm3+/Tb3+/Sm3+ tri-doped Na5Y9F32 single crystal may provide a promising candidate for white light-emitting diodes, luminescent materials and fluorescent display devices.