Shining Mn⁴⁺ in 0D Organometallic Fluoride Hosts towards Highly Efficient Photoluminescence

Abstract The design and discovery of Mn⁴⁺‐activated fluoride phosphors that can secure both high luminescence efficiency and short fluorescence lifetime simultaneously are crucial and urgent for constructing high‐quality wide‐color gamut (WCG) backlight display applications. Herein, a series of brand‐new Mn⁴⁺‐activated narrow‐band red‐emitting phosphors with both high external quantum efficiency (EQE, >50%) and short fluorescence lifetime (τ ≤ 3.8 ms) are designed by introducing Mn⁴⁺ into newfound tetramethylammonium (Me₄N)‐based organometallic fluoride (Me₄N)₂BF₆ (B = Ge, Ti, Zr) hosts. These intriguing properties of Mn⁴⁺ arise from the larger steric hindrance of (Me₄N)⁺ cations and low local structure symmetry in the 0D (Me₄N)₂BF₆, as verified by the structural and spectral analyses. (Me₄N)₂GeF₆:Mn⁴⁺, as a representative, shows a high EQE of ≈64.6% and a short lifetime of ≈3.78 ms. A prototype projector with superb performance is assembled by employing a remote (Me₄N)₂GeF₆:Mn⁴⁺‐based white light‐emitting diode with high luminous efficiency (≈143.09 lm W⁻¹) and WCG (≈112.02% National Television System Committee (NTSC)) to demonstrate their great potentials for backlight applications. The research brings up a promising alternative as the host materials for Mn⁴⁺‐doped fluoride phosphors and provides a deeper understanding on the correlation between structure and luminescence.