Upconversion luminescence of holmium and ytterbium co-doped yttrium oxysulfide phosphor

The upconversion optical characteristic and brightness of Y2O2S:Yb,Ho phosphors are investigated. It is shown that Y2O2S:Yb,Ho exhibits NIR, red, green, blue and even ultraviolet-blue emission bands under 980 nm pumping. Moreover, Y2O2S:Yb,Ho shows excellent upconversion luminescence and its upconversion brightness is 2.2 times to that of the commercial Y2O2S:Yb,Er phosphors. The upconversion mechanism is discussed: the green and NIR emissions are due to two consecutive energy transfer from Yb3+ to Ho3+, and the blue and red emissions can be explained as a loop-like mechanism.