Thermally stable near-infrared emission from a double perovskite K2LiScF6:Cr3+ phosphor for light-emitting diodes

The exploration of Cr3+-doped near-infrared (NIR) phosphors for light-emitting diodes has attracted widespread attention. In this work, we present a fluoride double perovskite K2LiScF6:Cr3+ NIR-emitting phosphor through a co-precipitation method. It was found that the Cr3+ activators undergo a weak crystal field and present a NIR emission band peaking at 768 nm under blue light excitation (430 nm). Meanwhile, the K2LiScF6:Cr3+ exhibits a high activation energy (0.537 eV), a weak electron-phonon coupling (EPC) effect and a remarkable photoluminescence thermal stability at 423 K, with an intensity of 95.1% of that at room temperature. Profiting from the luminescent properties, clear night vision images and human palm vein photographs were realized by coating the K2LiScF6:Cr3+ phosphor on a blue InGaN chip and using it as a lighting source, suggesting its applicability in light-emitting diodes for NIR spectroscopy applications.