Comparative Investigation on Upconversion Luminescence Properties of Lu2O3:Er/Yb and Lu2O2S:Er/Yb Phosphors

Abstract

A series of (Lu0.99−xEr0.01Ybx)2O3 and (Lu0.99−xEr0.01Ybx)2O2S (x = 0—0.1) phosphor particles are prepared to investigate their upconversion luminescence properties. Under 980 nm pumping laser, the two phosphors both exhibit strong green emission at ≈520—573 nm and weak red emission at ≈648—688 nm arising from 4S3/2/2H11/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+, respectively. The optimum concentrations of Yb3+ sensitizers are found to be 1.0 at% in oxide and 0.5 at% in oxysulfide, and their corresponding CIE chromaticity coordinates are (0.29, 0.69) and (0.33, 0.65). The Lu2O2S:Er/Yb phosphor exhibits ≈42 times higher luminescence intensity than the Lu2O3:Er/Yb contrast. More Yb3+ addition further increases the proportion of red emission by the cross‐relaxation between adjacent Yb3+ and Er3+ and the multiphonon relaxation. The luminescence intensities of the two phosphors gradually increase as the laser output power increases and the upconversion mechanisms are both identified to be two‐phonon processes. The Lu2O2S:Er/Yb phosphor has a shorter lifetime than the Lu2O3:Er/Yb counterpart, whereas the lifetime for the red emission is longer than that for the green emission in each case.