A Nontoxic and Environmentally Friendly NIR-II Phosphor for Night Vision, Bio-Imaging, Large-Scale Detection, and Information Anti-Counterfeiting with High-Resolution Imaging

Near-infrared second region (NIR-II, 1000–1600 nm) has deeper penetration depth, higher sensitivity, and spatial resolution than NIR first region (NIR-I, 700–1000 nm). However, Cr 3+ and Ni 2+ -doped NIR-I/NIR-II phosphor with serious pollution and toxicity issues pose limitations for the application of these phosphors. Here, the Fe 3+ -doped Cs 2 NaLuCl 6 is reported by grinding-sintering method, which shows the broadband emission in the range of 1000–1600 nm with a FWHM of ≈309 nm, while the PLQY as 17.29%, under 395 nm excitation. The unique broadband emission of this phosphor originates from the activation center of Fe 3+ located in an environment with an extremely weak octahedral crystal field provided by the Cs 2 NaLuCl 6 lattice. A NIR pc-LED device is assembled with the optimal phosphor encapsulated with a commercially available 395 nm ultraviolet LED chip. Which shows a NIR output of 23.5 mW and an electro-optical conversion efficiency of 6.53% under 100 mA driving current, while the potential application of NIR pc-LED is demonstrated in the field of night vision, bio-imaging, large-scale detection, and information anti-counterfeiting with high-resolution imaging.