Highly efficient red emission and multiple energy transfer properties of Dy3+/Mn4+ co-doped Ca14Zn6Ga10O35 phosphors

Abstract

Novel Dy³⁺/Mn⁴⁺ co-doped Ca₁₄Zn₆Ga₁₀O₃₅ phosphors have been synthesized by a solid state reaction technique. Strong blue emission ranging from 370 nm to 500 nm was observed for the Ca₁₄Zn₆Ga₁₀O₃₅ host, attributed to the recombination of a donor–acceptor pair through a tunneling process. High internal and external quantum efficiencies of 64.4% and 56.2% respectively were obtained under the excitation of 310 nm in Mn⁴⁺ doped Ca₁₄Zn₆Ga₁₀O₃₅. This external quantum efficiency is the highest one reported for Mn⁴⁺ doped oxides. The temperature-dependent quantum efficiency of Ca₁₄Zn₆Ga₁₀O₃₅:Mn⁴⁺ is also measured, indicating the unchanged absorption of the excitation light with temperature. In Ca₁₄Zn₆Ga₁₀O₃₅:Dy³⁺, Mn⁴⁺ phosphors, multiple energy transfer from the host to Dy³⁺ and from Dy³⁺ to Mn⁴⁺ is observed and is confirmed to be a result of the dipole–dipole interaction. The emission changes from deep blue to white to deep red according to the different Dy³⁺/Mn⁴⁺ concentration ratio, and the warm white emission can be realized with the chromaticity coordinate (0.345, 0.275), CCT 3525 K and CRI 87. These results suggest that Ca₁₄Zn₆Ga₁₀O₃₅:Mn⁴⁺ phosphors have potential application as high efficiency red phosphors for solid-state lighting, while Dy³⁺/Mn⁴⁺ co-doped Ca₁₄Zn₆Ga₁₀O₃₅ phosphors can be used as a single-phased white phosphor.