Down-shifting by energy transfer in Tb3+/Dy3+ co-doped zinc phosphate glasses

An optical spectroscopy investigation of zinc phosphate glasses activated with Tb3+/Dy3+ ions is carried out through photoluminescence spectra and decay time measurements. The emission color can be adjusted from yellow-green light, with CIE1931 chromaticity coordinates (036,0.44), toward the white light region (035,039) by decreasing the Tb3+ content from 1.0 to 0.1 mol% of Tb(PO3)(3) upon Dy3+ excitation at 423 nm. Such visible region luminescence is generated by D-5(4)-> F-7(5) and D-5(4)-> F-7(3) emissions of Tb3+ in addition to I-4(15/2)-> H-6(15/2), F-4(9/2)-> H-6(15/2), F-4(9/2)-> H-6(13/2) and F-4(9/2)-> H-6(11/2) emissions of Dy3+, so that Tb3+ emission is sensitized by Dy3+ through a non-radiative resonant energy transfer. A dominant D-5(4)-> F-7(5) green emission is observed in detriment of the D-5(3)-> F-7(j) blue emissions upon 282 nm excitation, as well as an extended excitation range (280-500 nm), due to multiple Dy3+ and Tb3+ transitions, which might contribute to enhance the spectral response of solar photovoltaic cells by down-shifting of the incident solar spectrum. (C) 2015 Elsevier B.V. All rights reserved.