Eu2+‐Doped Layered Double Borate Phosphor with Ultrawide Near‐Infrared Spectral Distribution in Response to Ultraviolet–Blue Light Excitation

Abstract

AbstractUltrabroadband near‐infrared (NIR) luminescent materials are important components for compact light sources used in food testing, medical and biosensing applications. A major long‐term challenge facing NIR luminescent materials is to design ultrabroadband phosphors activated by the rare‐earth ions characterized by the f–d transition. Here, an Eu2+‐doped Ba3Lu(BO3)3 phosphor, showing peculiar luminescence characteristics such as a long emission wavelength ≈720 nm, a broader full width at half maximum of ≈197 nm, a large Stokes shift of ≈8300 cm–1, and a longer decay time ≈5.58 µs, is reported. The smaller Eu2+ occupy the irregular and larger Ba2+ sites further reducing the symmetry, resulting in the increased splitting of the degenerate 5d level, thereby lowering the energy of Eu2+ emission. The longer decay time is also associated with the irregular Ba sites. This work improves the NIR mechanism of Eu2+ and opens up a new idea for exploring promising broadband NIR luminescent materials.