Defect-related luminescence behavior of a Mn⁴⁺ non-equivalently doped fluoroantimonate red phosphor

Non-equivalent or non-octahedral substitution is a crucial strategy to gain Mn⁴⁺-doped fluoride red phosphors with a short fluorescence lifetime, whereas the impact of their structural defects on the photoluminescence (PL) properties remains unrevealed. Here, a non-equivalently doped RbSbF₆:Mn⁴⁺ (RSFM) with a high quantum efficiency of 88% and a thermal stability of 121% at 425 K is newly reported to probe the defect-related PL behavior. Formation energy calculations imply that an interstitial defect was formed to balance the charge and stabilize the crystal structure. Concentration-dependent decay studies reveal that Mn⁴⁺ emission is quenched mainly by energy transfer to a neighboring defect . The large ionic radius of Sb⁵⁺ and defect leading to a premature optimal doping (0.11 mol%) is demonstrated by the refined contrast of the crystal structure and substitution mode among various Mn⁴⁺-doped prototypes. A couple of medium ⁴T₂ state energies and the energy difference between the Mn⁴⁺ level with the valence band maximum enable its superior thermal stability. A higher defect concentration slightly aggravates this thermal quenching. Using the RSFM red phosphor in a white light-emitting diode offers a wide-color-gamut of 121% NTSC for backlight displays. This work would provide a new perspective to understand the defect effect on the PL behavior of special Mn⁴⁺ asymmetrically doped fluorides.