LAUSR

Abstract We studied composite ZnO:Y 2 O 3 matrix for upconversion luminophore pair Er:Yb using near IR light excitation. Uni-phase crystalline nanoparticles were produced up to a 4% co-doped ZnO in Y 2 O 3 . In ZnO:Y 2 O 3 co-host matrix, Er(2%):Yb(10%) pair emits strong red luminescence. Doping 4% ZnO into the matrix enhances the luminescence by ~ 2.5 times. The mechanisms for the predominant red emission in the presence and absence of Zn ions were studied. An energy back transfer (EBT) process from Er to Yb is the main pathway for the intense red emission under NIR excitation although other mechanisms, e.g. Er-Er cross relaxation (CR), may also contribute to the red emission. The Er-Yb EBT process brings the Er ion from the green emission state to the intermediate 4 I 13/2 state, which further absorbs a near IR photon and jumps to the red emission state. The introduction of ZnO into Y 2 O 3 matrix does not interfere with this process significantly. Thus, the enhancement of luminescence is mainly caused by the breaking of the symmetry around Er 3+ ions due to the Y-to-Zn substitution, which favors the f - f electric dipole transitions that are forbidden in centrosymmetric environment.