Synthesis and spectroscopy of color tunable Y2O2S:Yb3+,Er3+ phosphors with intense emission

Trivalent ytterbium and erbium doped in yttrium oxysulfide (Y2O2S:Yb3+,Er3+) phosphors were synthesized by solid state flux fusion method and their upconversion spectral properties were studied as a function of different Yb3+ concentrations. The solid state flux fusion results in well crystallized hexagonal shaped phosphor particles with an average size of 3.8 mu m. The detailed optical characterizations such as absorption, emission, and fluorescence decay were performed to explore the emission processes in the UV-VIS-NIR as well as to quantitatively estimate the fluorescence quantum yield. Upconversion spectral studies show that for all the compositions, green emissions are stronger; in particular the green emission intensity is 1.7 times stronger than the red intensity with composition of 9 mol% Yb3+ and 1 mol% Er3+. Mechanisms of upconversion by two-photon and energy transfer processes are interpreted and explained. The color coordinates are measured and the color tunability was analyzed as a function of the 980 nm excitation power. Results show that the Y2O2S:Yb3+,Er3+ phosphor offers power dependent color tuning properties where the emission color can be tuned from 490 to 550 nm by simply changing the 980 nm excitation power from 10 to 50 mW. (C) 2011 Elsevier B.V. All rights reserved.