Expanding near-infrared emission bandwidth in K2NaCrF6:Fe3+ phosphors through dipole-dipole energy transfer

Currently, the application potential of Cr 3+ doped near-infrared (NIR) fluoride phosphors excited by blue light is promising. However, the development of near-infrared fluoride phosphors with wider emission bandwidth remains a challenge. Herein, we employed the hydrothermal method to prepare K 2 NaCrF 6 :Fe 3+ phosphors. Upon excitation at 432 nm, the K 2 NaCrF 6 :xFe 3+ phosphors exhibited broad near-infrared emission, with the main peak ranging from 752 nm to 780 nm. As the Fe 3+ concentration increased, the luminescence intensity of the K 2 NaCrF 6 :xFe 3+ phosphor decreased, accompanied by a redshift in the emission band and an increase in the full width of the emission spectrum half-peak. These changes can be attributed to the dipole-dipole interaction, specifically the energy transfer between Fe 3+ and Cr 3+ , leading to the 4 T 2 ( 4 F) → 4 A 2 (Cr 3+ ) and 4 T 1 ( 4 G) → 6 A 1 ( 6 S) (Fe 3+ ) transitions.