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.
Keywords: Fe3+ doping; NIR emission; afterglow; energy-level alignment; night vision.