Engineering Efficient Long‐Wavelength Broadband NIR Persistent Luminescence for Multifunctional Applications

ABSTRACT Near‐infrared (NIR) persistent luminescent (PersL) materials hold significant promising applications in fields such as bioimaging and information storage. However, existing high‐performance Cr 3+ ‐doped NIR PersL materials generally suffer from relatively short emission wavelengths and narrow spectral bandwidths. Herein, we report an optimized Cr 3+ ‐doped Na 2 CaSn 2 Ge 3 O 12 (NCSGO:Cr 3+ ) phosphor that exhibits long‐wavelength broadband NIR PersL, with a PersL peak wavelength of 815 nm, a PersL bandwidth of 124 nm, and a PersL duration exceeding 80 h. Notably, the undoped NCSGO host exhibits self‐activated NIR PersL, while Cr 3+ doping not only further redshifts the emission peak and broadens the emission band but also significantly enhances PersL brightness, duration, and excitation flexibility. A systematic investigation into the electron charging processes and trap distributions elucidates the underlying PersL mechanisms in both the NCSGO host and the Cr 3+ ‐activated systems. Leveraging the superior PersL property of NCSGO:Cr 3+ , the practical potential in night‐time information reading, information encryption, and deep‐tissue penetration imaging has been demonstrated, showcasing its versatility for advanced optical applications. This work presents a strategy for Cr 3+ doping to tailor efficient long‐wavelength broadband NIR PersL and underscores its multifaceted potential in cutting‐edge photonic technologies.