Red–green–blue upconversion luminescence and energy transfer in Yb3+/Er3+/Tm3+ doped YP5O14 ultraphosphates

Abstract

Red, green, and blue emissions through up conversion and energy transfer processes were investigated in triply doped YP5O14: Yb3+, Er3+, Tm3+ ultraphosphates upon excitation at 980nm as a function of the Yb3+, Er3+ and Tm3+ concentrations. Highly crystalline tri-doped samples showing a monoclinic form with C2/c space group symmetry were synthesized by a flux method leading to the elaboration of single crystals which were crushed for physical-chemical mainly by X-ray powder diffraction and optical up conversion characterization.The blue, green and red emissions intensity can be adjusted by the Yb3+, Er3+ and Tm3+ amounts. The Er3+ red and green up conversion emissions were examined in the case of the Yb3+/Er3+ co-doped YP5O14 materials. Two- and three-photons processes are observed for the red and green emissions of Er3+ respectively. Three visible red, green and blue up conversion emissions corresponding to Er3+4F9/2→4I15/2 (red), Tm3+1G4→3F4; 3F2,3→3H6 (red), Er3+2H11/2, 4S3/2 →4I15/2 (green) and Tm3+1G4 → 3H6 (blue) emission bands were simultaneously observed in triply doped YP5O14: Yb3+, Er3+, Tm3+ ultraphosphates due to Yb–Er and Yb–Tm up conversion mechanisms. Moreover, a three-photon process is observed for the red emission in the tri-doped materials instead of a 2-photons mechanism observed for samples without Tm, due to a Er3+→ Tm3+ energy transfer involving the Er3+4F9/2 and the Tm3+3F2,3 states.Despite the presence of large phonons energy due to the phosphate material, around 1200cm−1, Er3+ and Tm3+ visible emissions due to up conversion phenomena can be subsequently combined in order to obtain a white light and find new applications in display devices.