High upconversion quantum yield at low pump threshold in Er3+/Yb3+ doped La2O2S phosphor

In this letter, we report the absolute upconversion quantum yields (QY) for 9% Yb3+ and 1% Er3+ co-doped La2O2S and its comparison with NaYF4 doped with 20% Yb3+, 2% Er3+ for all the upconversion emissions centered at 410, 550, 667, and 822 nm at various excitation power densities at 977 nm excitation. The maximum upconversion QY for 9% Yb3+ and 1% Er3+ co-doped La2O2S was measured to be 5.83±0.87% at the excitation power density of 13 W/cm2. An excitation power dependent study revealed that although absolute upconversion QY measured for NaYF4: 20% Yb, 2% Er is higher at higher excitation power densities, La2O2S: 9% Yb, 1% Er possesses higher QYs at the lower excitation power densities.

► The absolute upconversion quantum yield (QY) measurements for 9% Yb3+ and 1% Er3+ doped La2O2S at various pump power densities at 977 nm excitation have been reported.
► Near-infrared (977 nm) to near-infrared (822 nm) and UV (410 nm) absolute upconversion QY for NaYF4:20% Yb, 2% Er has been reported for the first time.
► The maximum upconversion QY for 9% Yb3+ and 1% Er3+ co-doped La2O2S was measured (5.83±0.9%) at the excitation power density of 13 W/cm2.