Broad-band sensitized visible up-conversion in Y2Mg3Ge3O12:Ni2+,Er3+,Nb5+ phosphors

Abstract

Ni²⁺, Er³⁺, Nb⁵⁺ tri-doped Y₂Mg₃Ge₃O₁₂ phosphors have been fabricated using a conventional solid-phase reaction method. Near infrared light in the wavelength range of 900–1700 nm can be up-converted by the phosphors into visible emissions peaking at 532 nm, 555 nm and 675 nm of Er³⁺, performed by the Ni²⁺ → Er³⁺ and Er³⁺ → Er³⁺ energy transfers. The introduction of Nb⁵⁺ ions can adjust the local environment of Ni²⁺ and Er³⁺ ions and thus effectively reduces their nonradiative transition probability, which largely enhances the intensity of up-conversion emission. The effects of Ni²⁺ and Er³⁺ concentration together with the excitation power on the fluorescence properties have been investigated. The Y₂Mg₃Ge₃O₁₂:0.015Ni²⁺,0.13Er³⁺,0.06Nb⁵⁺ phosphor manifests the optimal UC emission effectiveness in this work, in which the energy transfer sensitization from Ni²⁺ → Er³⁺ induced by quadrupole-quadrupole interaction is as high as 92.1%. The developed broadband near-infrared excitable up-conversion materials are promising for extensive photonic applications, including c-Si solar cells and infrared detectors.