Luminescence properties and spectral modulation of the ultra-broadband, highly efficient near-infrared luminescent material CaGa4O7:Cr3+, Cr4+, Yb3+

Recently, near-infrared phosphors have received a lot of attention due to their wide application in the field of detection and analysis, and it is urgent to develop efficient broadband NIR phosphors. In this paper, a conventional high-temperature solid-phase method was used to prepare a novel near-infrared phosphor CaGa 4 O 7 :Cr 3+ , Cr 4+ , which provides two emission bands ranging from 600 to 1000 nm and 1100–1600 nm. Although there are only four and five coordination sites in the CaGa 4 O 7 (CGO) lattice, the doping of the Cr 3+ ions in the CGO causes the Ga–O tetrahedral distortion into an octahedron , providing a favorable environment for the emission of the Cr 3+ ions. Under blue light excitation, Cr 3+ emits luminescence in the NIR I region from 600 to 1000 nm with a half-height width of up to 148 nm. With increasing Cr ion concentration , more and more Cr 4+ preferentially occupy the four coordinated Ga 3+ sites, and the intensity of the ultra-broad emission band in the NIR II region (1100 nm–1600 nm) increases with a full width at half maximum (FWHM) of 262 nm. To further optimize the emission spectrum , Yb 3+ was codoped into CGO: Cr 3+ , Cr 4+ , the energy transfers from Cr 3+ to Yb 3+ in CGO was found, thus filling the gap between 1000 and 1100 nm in the CGO emission spectrum and obtaining a more complete ultra-wide spectrum. Moreover, the luminescence mechanism, energy transfer efficiency, and quantum yield are also studied in detail, and the ability of CaGa 4 O 7 :Cr 3+ , Cr 4+ , and Yb 3+ luminescent materials to achieve ultra-broadband efficient near-infrared emission was demonstrated.