Advances in Chromium-Activated Phosphors for Near-Infrared Light Sources

Cr3+/Cr4+-activated near-infrared (NIR) luminescent materials have attracted extensive attention owing to their tunable emission wavelength and widespread applications in plant growth, food analysis, biomedical imaging, night vision, and so on. Plenty of excellent NIR materials are developed by introducing Cr3+/Cr4+ ion to various inorganic hosts. Herein, the effect of crystal field on Cr3+/Cr4+ luminescence by combining the Tanabe-Sugano energy level diagram and configuration coordinate model is discussed. Research progress of Cr3+/Cr4+-doped NIR luminescent materials, including the phosphors designed from structural models with octahedral, tetrahedral, and other coordination types, is then outlined. The luminescence properties of more than 200 kinds of Cr3+/Cr4+-doped materials are summarized. In particular, several strategies for tuning emission wavelength, broadening emission band, enhancing NIR luminescence efficiency, and improving thermal stability, are listed. Finally, the current challenges and future prospects in the research of Cr3+/Cr4+-doped NIR luminescent materials are presented. This review will contribute to a deeper understanding of not only Cr3+/Cr4+ luminescence mechanism but also the current research progress of chromium-doped luminescent materials, so as to develop more Cr3+/Cr4+-activated NIR luminescent materials with better performance and explore more applications.

Automated summary

This review discusses the effect of crystal field on the luminescence of Cr3+/Cr4+ and outlines the research progress of Cr3+/Cr4+-doped NIR luminescent materials. It summarizes the luminescence properties of these materials and lists strategies for tuning emission wavelength, broadening emission band, enhancing NIR luminescence efficiency, and improving thermal stability. Finally, it presents the current challenges and future prospects in the research of Cr3+/Cr4+-doped NIR luminescent materials.