Absolute quantum yield measurements in Yb/Ho doped M2O2S (M=Y, Gd, La) upconversion phosphor

Using the integrating sphere technique the absolute quantum yield measurements of the visible emission bands at 550, 650 and 750 nm in Yb/Ho doped M2O2S (M=Y, Gd, La) upconversion phosphor have been reported for the first time. Observations show that the 750 nm emission in La2O2S doped with 1 mol% each of Yb and Ho yield the highest efficiency of 0.12% followed by green emission which is 0.065% with 9.5% Yb and 0.5% Ho in the same host. The red emission in La2O2S, Y2O2S are nearly 6 times weaker than green emission, whereas in Gd2O2S it is 14 times less efficient making Gd2O2S doped with 4.5 mol% Yb and 0.5 mol% Ho as the most efficient single color green upconvertor among all three host compositions studied.

► Upconversion efficiency of YbHo doped metal oxysulphide was measured for the first time.
► 756 nm emission band shows the highest efficiency in all phosphors under 980 nm excitation.
► Gd2O2S:Yb(4.5%)/Ho(0.5%) shows the best green upconversion efficiency.
► Green upconversion efficiency shows increasing tendency with Yb/Ho ratio in YOS and LOS.