Darkness‐Penetrating NIR Afterglow from Cr ³⁺ ‐Doped Phosphors for Remote Target Surveillance

Abstract Achieving excitation‐free, long‐range target surveillance under complete darkness remains a critical challenge for night‐vision technology. Here, a breakthrough is reported in near‐infrared (NIR) persistent luminescence (PersL) materials designed specifically for this frontier. Through strategic bandgap engineering via Sm ³ ⁺ co‐doping and In ³ ⁺ solid‐solution incorporation in the novel Cr ³ ⁺‐doped Mg ₃ Ga _1.9 In _0.1 SnO ₈ spinel phosphor, the afterglow intensity and duration are dramatically enhanced. The optimized material exhibits an ultra‐long NIR PersL exceeding 168 h. Crucially, PDMS films embedded with this phosphor enabled real‐time, persistent target detection at an unprecedented distance of 47.5 m in complete darkness, entirely without any external excitation source. This record‐setting long‐range performance demonstrates the material's potential as an enabling technology for passive, long‐range nighttime surveillance systems. Comprehensive spectroscopic studies elucidate the underlying PersL mechanism. This work establishes a new pathway for designing ultra‐long NIR PersL materials and paves the way for advanced applications in remote night‐vision technologies.