Near-Infrared Long Afterglow in Fe³⁺-Activated Mg₂SnO₄ for Self-Sustainable Night Vision

The advent of near-infrared (NIR) afterglow in Cr³⁺-doped materials has stimulated considerable interest in technological applications owing to the sustainable emission of light with good penetrability. However, the development of Cr³⁺-free NIR afterglow phosphors with high efficiency, low cost, and precise spectral tunability is still an open question. Herein, we report a novel Fe³⁺-activated NIR long afterglow phosphor composed of Mg₂SnO₄ (MSO), in which Fe³⁺ ions occupy the tetrahedral [Mg-O₄] and octahedral [Sn/Mg-O₆] sites, giving rise to a broadband NIR emission spanning 720-789 nm. On account of energy-level alignment, the electrons released from the traps show a preferential return to the excited energy level of Fe³⁺ in tetrahedral sites through tunneling, leading to a single-peak NIR afterglow centered at 789 nm with a full-width at half-maximum (fwhm) of 140 nm. The high-efficiency NIR afterglow, showing a record persistent time lasting over 31 h among Fe³⁺-based phosphors, is demonstrated as a self-sustainable light source for night vision applications. This work not only provides a novel Fe³⁺-doped high-efficiency NIR afterglow phosphor for technological applications but also establishes practical guidance for rational tuning of afterglow emissions.