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

To settle the unsatisfied efficiency of near-infrared (NIR) emission in lanthanide-doped luminescent materials, a series of Pt⁴⁺-doped and Pt⁴⁺/Er³⁺-codoped Cs₂ZrCl₆ double perovskite phosphors are designed. Excited by 254 nm, Pt⁴⁺-doped Cs₂ZrCl₆ compounds can exhibit the characteristic emissions of host and Pt⁴⁺, resulting in the polychromatic luminescence caused by the efficient energy transfer from host to Pt⁴⁺. 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 [PtCl₆]²⁻ octahedron. Furthermore, compared with that of Er³⁺-doped sample, the intensity of the NIR-II emission of Er³⁺ at 1540 nm in Pt⁴⁺/Er³⁺-codoped Cs₂ZrCl₆ double perovskite phosphors is greatly improved, namely, a 127-fold increase, due to efficient energy transfer from host and Pt⁴⁺ to Er³⁺. Furthermore, the quantum efficiencies of the visible and NIR-II emissions in Cs₂ZrCl₆:0.6%Pt⁴⁺/25%Er³⁺ 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 Er³⁺ in double perovskite phosphors can be efficiently regulated via using multi-channel composite energy transfer engineering.