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

Near-infrared (NIR) persistent luminescent (PersL) materials hold significant promising applications in fields such as bioimaging and information storage. However, existing high-performance Cr³⁺-doped NIR PersL materials generally suffer from relatively short emission wavelengths and narrow spectral bandwidths. Herein, we report an optimized Cr³⁺-doped Na₂CaSn₂Ge₃O₁₂ (NCSGO:Cr³⁺) 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 Cr³⁺ 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 Cr³⁺-activated systems. Leveraging the superior PersL property of NCSGO:Cr³⁺, 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 Cr³⁺ doping to tailor efficient long-wavelength broadband NIR PersL and underscores its multifaceted potential in cutting-edge photonic technologies.