Near‐Infrared II to III Light Source Enabled by a Laser‐Activated Flexible Film

ABSTRACT Photons in the near‐infrared third region (NIR‐III, 1600–2300 nm) have extremely low tissue absorption and scattering, and nearly no autofluorescence background in biological tissues for deep optical imaging. Currently, the emission bandwidth for most NIR phosphors is below the NIR‐III region, and their full width at half maximum (FWHM) are relatively narrow, which significantly constrains the application as broadband NIR‐III emitting. In this work, Ni 2 + ‐doped Ba 2 La 2 ZnW 2 O 12 NIR phosphors with a close‐packed hexagonal structure were prepared, which exhibited broadband emission ranging from 1200 to 2000 nm, a peak emission at 1530 nm, with an FWHM of approximately 300 nm, and an internal quantum efficiency of 41.22% under 330 nm excitation. Experimental analysis and numerical simulation showed that the mechanism of this unique broadband NIR‐III emission of this phosphor is primarily due to an orbital hybridization between Ni 2+ and O 2− in the octahedra, which creates impurity energy levels and participates in the radiative transition pathways. The Ba 2 La 2 ZnW 2 O 12 :Ni 2+ was encapsulated in a flexible PDMS film to form a laser‐activated NIR device capable of emitting NIR‐III with high‐energy density, and its demonstrated potential applications in NIR‐based long‐range monitoring and anti‐counterfeiting information encryption. Our discovery provides a basis to explore new broadband NIR‐III phosphor and their applications.