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

Abstract Broadband near‐infrared (NIR) phosphors have garnered significant attention due to their potential applications in phosphor‐concerted NIR light‐emitting diodes (pc‐NIR‐LEDs). Cr 3+ ‐doped NIR phosphors are particularly intriguing because of their broad NIR emission and high efficiency. However, reports on Cr 3+ ‐doped NIR‐II (900–1700 nm) phosphors are scarce. In this study, a novel Cr 3+ ‐doped SrLaGa 3 O 7 NIR‐II phosphor is presented, where the Cr 3+ ions are located at tetrahedral sites. The full width at half maximum (FWHM), peak wavelength, internal quantum efficiency (IQE), and thermal activation energy (Δ E ) for the synthesized SrLaGa 3 O 7 :0.9%Cr 3+ phosphor are 194 nm, 1167 nm, 76.12%, and 0.269 eV, respectively. The substitution of Sc 3+ for Ga 3+ enhances the luminescence performance, and the 0.9%Cr 3+ /3%Sc 3+ co‐doped SrLaGa 3 O 7 phosphor exhibits a peak wavelength of 1208 nm, an IQE of 92.78%, and a Δ E of 0.285 eV. Furthermore, the sintering process in the air induces a transition from Cr 3+ to Cr 4+ , resulting in the formation of SrLaGa 3 O 7 :0.9%Cr 4+ phosphor, which has a peak wavelength of 1270 nm and an FWHM of 305 nm. The potential application of the 0.9%Cr 3+ /3%Sc 3+ co‐doped SrLaGa 3 O 7 phosphor in pc‐NIR‐LEDs is also evaluated.