Broadband NIR-II Emission Generated by Tetrahedral Cr3+/Cr4+ in SrLaGa3O7

Broadband near-infrared (NIR) phosphors have garnered significant attention due to their potential applications in phosphor-concerted NIR light-emitting diodes (pc-NIR-LEDs). Cr3+-doped NIR phosphors are particularly intriguing because of their broad NIR emission and high efficiency. However, reports on Cr3+-doped NIR-II (900-1700 nm) phosphors are scarce. In this study, a novel Cr3+-doped SrLaGa3O7 NIR-II phosphor is presented, where the Cr3+ ions are located at tetrahedral sites. The full width at half maximum (FWHM), peak wavelength, internal quantum efficiency (IQE), and thermal activation energy (Delta E) for the synthesized SrLaGa3O7:0.9%Cr3+ phosphor are 194 nm, 1167 nm, 76.12%, and 0.269 eV, respectively. The substitution of Sc3+ for Ga3+ enhances the luminescence performance, and the 0.9%Cr3+/3%Sc3+ co-doped SrLaGa3O7 phosphor exhibits a peak wavelength of 1208 nm, an IQE of 92.78%, and a Delta E of 0.285 eV. Furthermore, the sintering process in the air induces a transition from Cr3+ to Cr4+, resulting in the formation of SrLaGa3O7:0.9%Cr4+ phosphor, which has a peak wavelength of 1270 nm and an FWHM of 305 nm. The potential application of the 0.9%Cr3+/3%Sc3+ co-doped SrLaGa3O7 phosphor in pc-NIR-LEDs is also evaluated.