Energy transfer enhanced broadband near-infrared phosphors: Cr3+/Ni2+ activated ZnGa2O4–Zn2SnO4 solid solutions for the second NIR window imaging

Abstract

Near-infrared luminescent materials have attracted considerable interest because of their excellent performance in the field of optical imaging. Here, a series of Cr³⁺/Ni²⁺ co-doped near-infrared phosphors Zn_1+ySn_yGa_2−2yO₄ (ZSGO) were synthesized via a solid-state reaction. The phosphors show broad emissions in the range of 1100–1700 nm in the second NIR window. The emission intensity of Ni²⁺ could be greatly enhanced owing to the energy transfer from Cr³⁺ to Ni²⁺. The energy transfer mechanism was inferred from the excitation and emission spectra and the decay lifetime curve, which confirm that the primary process is the electric dipole–dipole interaction. In order to evaluate the potential optical imaging application, NIR-LED light source packages were fabricated with Cr³⁺/Ni²⁺ co-doped Zn_1+ySn_yGa_2−2yO₄ (ZSGO) phosphors and blue LED chips, which revealed high stability and a strong transilluminated biological tissue effect. These results indicate a great prospect in advanced optical imaging for NIR pc-LED applications.