Effect of Er3+ concentration on the upconversion luminescence of GdOCl:Er3+ powders with excitation of 514.5 nm

Abstract GdOCl phosphors doped with different Er 3+ concentration were prepared by modified solid state reaction. The structure and purity of the powders were analyzed by X-ray diffraction. Upconversion emissions from blue to violet to ultraviolet regions were observed with excitation of 514.5 nm. Power-dependence analysis demonstrated that the two-photon upconversion process populated the luminescent levels 4 G 11/2 , 2 P 3/2 , 2 H 9/2 , and 4 F 3/2, 5/2 . The energy distribution of upconversion spectra depends on doping concentration, and the intensity ratio between involved energy levels changed with increasing Er 3+ concentration. The dependence of spectral distribution on concentration was possibly ascribed to cross relaxation process of 2 P 3/2  +  4 I 15/2  →  4 I 13/2  +  2 H 9/2 . Besides the cross concentration, excited state absorption and energy transfer upconversion were proposed to be the possible mechanisms for upconversion.