Self-activated near-infrared luminescence in double perovskite CaLaMgSbO6 phosphors

Self-activated near-infrared (NIR) phosphors have garnered increasing attention in advanced light sources and biomedical applications owing to their simplified synthesis, cost-efficiency, non-toxicity, and especially the absence of extrinsic activator ions. However, developing efficient and thermally stable self-activated NIR phosphors remains a significant challenge for practical applications. Herein, a NIR phosphor Ca 0 · 95 LaMgSbO 6 (C 0.95 LMSO) (λex = 335 nm, λem = 710 nm) is synthesized employing a non-stoichiometric strategy, where interstitial oxygen (Oᵢ) defects are identified as the primary origin for the self-activated NIR luminescence through synergistic experimental and theoretical analyses. The controlled Ca 2+ deficiency promotes the generation of more Oᵢ defects, thereby enhancing the intensity of Oᵢ defect-induced near-infrared luminescence. Furthermore, the introduction of Bi 3+ sensitizers enables efficient energy transfer pathways, the optimized phosphor leading to exceptional photoluminescence quantum yield (68.1 %) and thermal stability (67.2 % intensity retention at 420 K). A fabricated NIR pc-LED based on Ca 0 · 95 LaMgSbO 6 :0.5 %Bi 3+ (C 0.95 LMSO: Bi 3+ ) phosphor exhibit promising performance in night vision and biomedical imaging applications. This study elucidates a defect-engineering paradigm grounded in oxygen interstitial defects, presenting a new research avenue for the development of high-performance self-activated NIR materials.