Site engineering strategy toward enhanced luminescence thermostability of a Cr3+-doped broadband NIR phosphor and its application

Abstract

Efficient broadband near-infrared (NIR) light sources are urgently needed for emerging applications in medicine, food analysis, and others. Nevertheless, the performance is limited by luminescence efficiency and thermostability in state-of-the-art broadband NIR phosphors. Here we demonstrate an effective strategy for achieving efficient and thermostable broadband NIR emission by site engineering in a SrGa₁₂O₁₉–LaMgGa₁₁O₁₉:Cr³⁺ system. Due to the structure symmetry promotion, the end-member SrGa₁₂O₁₉:Cr³⁺ shows excellent luminescence thermostability, i.e., higher luminescence quenching temperature and more remarkable color stability compared with LaMgGa₁₁O₁₉:Cr³⁺. At 500 K, the integrated PL intensity remains 86.5% of that at 290 K. Fine local structure, photoluminescence spectra and luminescence decay curves together support that the optically activated Cr³⁺ centers are reduced due to site symmetry change in SrGa₁₂O₁₉:Cr³⁺, leading to the remarkable luminescence thermostability. Finally, we have fabricated NIR pc-LEDs with commercial blue-light-emitting InGaN chips (450 nm), showing that SrGa₁₂O₁₉:Cr³⁺ has a high external quantum efficiency of 45% and has great potential in high-power and efficient pc-LED applications.