A novel broadband Ba3Ca4(BO3)3(SiO4)Cl:Mn4+ near-infrared phosphor with a special pseudo-octahedral Mn4+ coordination structure.

A pseudo-octahedral coordination structure of Mn4+ has been innovatively designed, which has realized the maximum red shift and the widest full width at half-maximum (FWHM) of Mn4+ emission so far, not only extending the emission wavelength of Mn4+ to the near-infrared (NIR) region, but also effectively broadening its bandwidth. In the Ba3Ca4(BO3)3(SiO4)Cl:Mn4+ (BCBSC:Mn4+) phosphor, the [Mn/Ca1O9] polyhedron contains one [Mn/Ca1O6] octahedron, which constitutes the pseudo-octahedral coordination structure of Mn4+. The BCBSC:Mn4+ phosphor can be excited at 362 nm and 470 nm and exhibits a broadband NIR emission centered at ∼756 nm with a super-wide range from 650 nm to 1100 nm. The FWHM can reach ∼90 nm. In addition, the internal quantum efficiency (IQE) of the BCBSC:0.01Mn4+ phosphor is 69.7%. The unique luminescence characteristics of BCBSC:Mn4+ phosphors are explored using experimental data and first principles calculation. The significant redshift, the abnormal broadband emission, and the high luminous efficiency are closely related to the special highly distorted [Mn/Ca1O6] pseudo-octahedral coordination environment. The results contribute to comprehending the mechanism of the broadband NIR emission of Mn4+ activated phosphors and broaden the research ideas of developing high-performance Mn4+ doped phosphors for NIR phosphor-converted light-emission diode applications.