Chromium(III)-Doped Fluoride Phosphors with Broadband Infrared Emission for Light-Emitting Diodes

Two types of infrared fluoride phosphors, Cr 3+ -doped K 3 AlF 6 and K 3 GaF 6, were developed in this research. The K 3 Al 1– x F 6: x Cr 3+ and K 3 Ga 1– y F 6: y Cr 3+ fluoride phosphors were proven to be pure phase via X-ray diffraction refinement, which demonstrated that the procedure can be applied to large-scale production. Electron paramagnetic resonance measurements indicated that Cr 3+ ions in cubic with respect to noncubic are coupled better with K 3 GaF 6 than with K 3 AlF 6 . The main differences between these two phosphors, the site symmetry and pressure behavior of the spectra, were obtained in temperature- and pressure-dependent spectra. According to the calculation results, Cr 3+ in fluorine coordination at ambient pressure indicates an intermediate crystal field. For the phosphor-converted light-emitting diodes (LEDs) fabricated from these two phosphors, the spectral range is from 650 to 1000 nm, which resulted in a radiant flux of 7–8 mW with an input power of 1.05 W. The research reveals detailed luminous properties, which will lead to a new way of studying Cr 3+ -doped fluoride phosphors and their application in LEDs.