Upconversion emission colour modulation of Y2O2S: Yb, Er under 1.55 μm and 980 nm excitation

• Y2O2S: Yb, Er shows excellent red emission under 1550 nm excitation exceeds.
• The adjustment of emission colour in a very wide range has been realized.
• Two-tone upconversion colour can be created.

The upconversion luminescence of Y2O2S: Yb, Er under 1550 nm pumping has been investigated. It presents excellent red emission under 1550 nm excitation with an upconversion brightness of more than twice that of Y2O3: Yb, Er under 980 nm excitation. Upconversion luminescence spectrum shows that the strongest NIR peak is situated at 1020 nm, the second strong peak is red emission centred at 690 nm, and the third strong peak is a green band. The red/green fluorescence branching ratio dramatically decreases with an increase in the Er3+ ion concentration or 1550 nm excitation power. Y2O2S: Yb, Er presents green upconversion luminescence under 980 nm excitation. Therefore, red and green two-tone upconversion colour can be created by 1550 and 980 nm excitation, respectively. Moreover, a very wide range of emission colour can be continuously tuned by the joint contribution of altered composition and excitation power.