Interstitial Oxygen Defect Inducing Near-Infrared Luminescence in Ca3La2W2O12 Phosphor

Self-activated near-infrared (NIR) phosphors have recently gained extensive attention in special illumination and biomedical applications owing to its non-toxicity, inexpensiveness and especially undoped luminescence center ions. However, high photoluminescence quantum yields (PLQY) and thermal stability remain challenges for NIR-emitting phosphors. In this study, a self-activated phosphor Ca₃La₂W₂O₁₂ (CLWO) successfully achieved a NIR emission and high thermal stability. Under 350 nm excitation, the optimal CLWO:0.2%Bi³⁺ phosphor shows a narrowband emission in the range of 650-800 nm and a full width of half maximum (FWHM) of 36 nm. Mechanism studies demonstrate that the interstitial oxygen within CLWO host can work as the luminescence center, and enables self-activated emission in NIR waveband. Moreover, CLWO:0.2%Bi³⁺ phosphor shows a high PLQY of 48.84% and excellent thermal stability (I_{420 K}/I_{300 K} = 69.09%). A NIR phosphor-converted LED (pc-LED) based on a Ca₃La₂W₂O₁₂:Bi³⁺ (CLWO:Bi³⁺) phosphor is fabricated on a 350 nm LED chip, demonstrating its potential in NIR night-vision monitoring. This work certainly designs novel insights for outstanding thermal stability of self-activated phosphors and develops new research avenues for self-activated NIR LED light sources applications.