Ultraintense Zero-Phonon Line from a Mn⁴⁺ Red-Emitting Phosphor for High-Quality Backlight Display Applications

The zero-phonon line (ZPL) of Mn⁴⁺, which highly depends on its local environment, is usually much weaker than the vibrational phonon sidebands. In this work, an ultraintense ZPL emission, coming from a brand new red-emitting Rb₂LiGaF₆:Mn⁴⁺ (RLGFM) phosphor upon blue light excitation, is presented. The interesting spectral characteristic originates from the nonequivalent substitution of Mn⁴⁺ for Ga³⁺ in a rigid octahedral structure with a low symmetry, which induces neighboring cation vacancies that distort the local symmetry of the [MnF₆] octahedra. Benefiting from the ultraintense ZPL emission, a wide color gamut is achieved using RLGFM and β-SiAlON:Eu²⁺ as color converters. Moreover, a comprehensive investigation on the thermal quenching behavior is also conducted to provide detailed insights to explore novel Mn⁴⁺ red phosphors for high-quality backlight display applications.