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

Abstract 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.