Tailoring of Visible‐NIR‐II Luminescence in Pt⁴⁺/Er³⁺‐Codoped Cs₂ZrCl₆ Double Perovskite Phosphors via Energy Transfer Engineering for Diversified Applications

Abstract To settle the unsatisfied efficiency of near‐infrared (NIR) emission in lanthanide‐doped luminescent materials, a series of Pt 4+ ‐doped and Pt 4+ /Er 3+ ‐codoped Cs 2 ZrCl 6 double perovskite phosphors are designed. Excited by 254 nm, Pt 4+ ‐doped Cs 2 ZrCl 6 compounds can exhibit the characteristic emissions of host and Pt 4+ , resulting in the polychromatic luminescence caused by the efficient energy transfer from host to Pt 4+ . Through combining the theoretical calculation and luminescence profiles, it is clear that the broadband emission at 660 nm is assigned to the self‐trapped exciton of [PtCl 6 ] 2− octahedron. Furthermore, compared with that of Er 3+ ‐doped sample, the intensity of the NIR‐II emission of Er 3+ at 1540 nm in Pt 4+ /Er 3+ ‐codoped Cs 2 ZrCl 6 double perovskite phosphors is greatly improved, namely, a 127‐fold increase, due to efficient energy transfer from host and Pt 4+ to Er 3+ . Furthermore, the quantum efficiencies of the visible and NIR‐II emissions in Cs 2 ZrCl 6 :0.6%Pt 4+ /25%Er 3+ double perovskite phosphor are 75.5% and 34%, respectively, excited by 254 nm. Additionally, via utilizing the designed phosphors, various applications including multilevel anti‐counterfeiting, non‐visual imaging, night vision, etc., are realized. This finding implies that NIR‐II emission of Er 3+ in double perovskite phosphors can be efficiently regulated via using multi‐channel composite energy transfer engineering.