Ab Initio Calculations Driven Discovery of BaLiF3:Mn4+ Fluoride Phosphor with Zero-Phonon Line Peak at 630.5 nm for Ultrawide Color Gamut Display

Abstract

The discovery of Mn⁴⁺-activated fluoride red phosphors with longer emission wavelength is crucial for ultrawide color gamut displays. However, since the emission of Mn⁴⁺ (²E → ⁴A₂) is constrained by the strong ionic interaction between Mn⁴⁺ and F^-, it is a significant challenge to tune the emission to meet the requirement of Recommendation BT.2020 (Rec. 2020) red-light standard (0.708, 0.292). Herein, density functional theory (DFT) calculations are utilized to determine the ²E emission energy of Mn⁴⁺ in fluorides; thus, a red phosphor BaLiF₃:Mn⁴⁺ with a record long-wavelength zero-phonon line (ZPL) emission at 630.5 nm and CIE chromaticity coordinates of (0.706, 0.294) is demonstrated. The apparent redshift of the emission of BaLiF₃:Mn⁴⁺ (ZPL = 630.5 nm) compared to that of commercial K₂SiF₆:Mn⁴⁺ (ZPL = 621 nm) is attributed to the high symmetry of the host lattice and the relatively strong electronegativity of the neighboring Li atoms around Mn⁴⁺. A prototype display device with an ultra-color gamut of 94.2% Rec.2020 is assembled by using the BaLiF₃:Mn⁴⁺ based white mini-LED backlight module. This study not only provides a promising candidate in the field of display, but also provides valuable references for accelerating the discovery of new and promising phosphors.