Luminescence enhancement in the Sr₂ZnW_1−xMo_xO₆:Eu³⁺,Li⁺phosphor for near ultraviolet based solid state lighting

A series of the Sr_1.9ZnW_1−xMo_xO₆:0.05Eu³⁺,0.05Li⁺phosphors was synthesized by high-temperature solid-state reaction method. The structure, ultraviolet-visible diffuse reflectance spectra, photoluminescence and decay properties of the phosphors were investigated as a function of the W/Mo ratio. All prepared mixed compounds have a cubic structure. The experimental spectroscopic results show the excitation bands of these phosphors is in the near ultraviolet region; the red-shift of these bands is observed upon increase of the Mo concentration. The strong red and weak orange-red emissions centered at 614 and 595 nm, respectively, were observed, which indicates that Eu³⁺occupies the non-centrosymmetric site. Co-doping with Mo can enhance the luminescent intensity and the optimal concentration was determined to be x = 0.4. Combination of the first-principles calculations with the experimental spectroscopic measurements confirmed an indirect band gap character for the prepared phosphors and allowed for estimation of their band gap value. The obtained results show that the Sr₂ZnW_1−xMo_xO₆phosphors have considerable potential for the near ultraviolet excited white light emitting diodes.