Strategy to optimize the broadband near-infrared emission based on Eu-doped sulfureted garnet phosphors toward emerging spectroscopy applications.

Eu-doped near-infrared (NIR) emitting phosphors, known for their high efficiency, broadband emission and spectral tunability, have gained much attention. However, achieving efficient NIR emission based on Eu remains a challenge due to the co-existence of Eu, especially in materials (i.e. garnets and apatites) containing trivalent lanthanide cations. In this study, a Eu doped sulfureted NIR-emitting garnet phosphor Ca(Sc, Eu)Si(O, S): Eu is successfully designed and synthesized. Notably, a strategy for regulating the initial valence state of dopants is proposed by using prepared EuS instead of the conventional EuO as raw material, enhancing the NIR emission by 135 %. Moreover, a sulfuration strategy is further introduced to enhance the NIR-emitting intensity and internal quantum efficiency by 192 % and 167.8 %, and to improve thermal stability by 154 % at 120 °C. The luminescence origin of the unusual broadband NIR emission is re-examined through chemical unit co-substitution strategy by introducing [AlHf] to replace [ScSi] ion pairs. Meanwhile, the spectral regulation and the performance optimization mechanism are systematically discussed. Finally, a green light pumped NIR LED device with a photoelectric efficiency of 9.43 %@100 mA and output power of 22.74 mW@100 mA is fabricated, showing remarkable potential in nondestructive testing and biomedical imaging applications.