White, yellow and reddish-orange light generation in lithium-aluminum-zinc phosphate glasses co-doped with Dy3+/Tb3+ and tri-doped with Dy3+/Tb3+/Eu3+

Abstract

A spectroscopic investigation of Dy3+/Tb3+ and Dy3+/Tb3+/Eu3+ doped lithium-aluminum-zinc phosphate glasses, focused on generation of tunable visible light, is performed through their photoluminescence spectra and decay time measurements. White, yellow and reddish-orange light emissions can be tuned with the excitation wavelength. In the Dy3+/Tb3+ co-doped glass emission of neutral white light of 4204 and 4517 K is achieved upon 393 and 348 nm excitations, respectively. The Dy3+/Tb3+/Eu3+ tri-doped glass can generate emission of warm white light of 3275 and 2866 K upon 348 and 446 nm excitations, respectively. The tri-doped glass can also generate yellow light of 2922 K with a high (577 nm) color purity of 98.1% upon 483 nm excitation, and reddish-orange light of 2235 K with a (604 nm) color purity of 96.3% upon 393 nm excitation, whose (0.641, 0.347) CIE1931chromaticity coordinates are close to those (0.67, 0.33) of the red phosphor proposed by the National Television Standard Committee. In the co-doped glass excited at 393 nm non-radiative energy transfer from Dy3+ to Tb3+ could be taking place into Dy3+-Tb3+ clusters, whereas in the tri-doped glass non-radiative energy transfers Dy3+→Tb3+/Eu3+ and Dy3+→Eu3+ through Tb3+ (upon 446 nm excitation), and Tb3+→Eu3+ (upon 483 nm excitation), could be occurring into Dy3+-Tb3+-Eu3+ clusters.