Multimode Luminescence with Temperature and Energy Level Synergistic Dependence in Rare Earth Halide DPs for Advanced Multifunctional Applications

Abstract Rare‐earth halide double perovskites (DPs) have attracted extensive attention due to their excellent optoelectronic performance. However, the correlation between luminescence performance, crystal structure, and temperature, as well as the inherent energy transfer mechanism, is not well understood. Herein, Lanthanide ions (Ln 3+ : Nd 3+ or Dy 3+ ) as the co‐dopants are incorporated into Sb 3+ doped Cs 2 NaYbCl 6 DPs to construct energy transfer (ET) models to reveal the effects of temperature and energy levels of rare earth on luminescence and ET. The different excited state structures of Sb 3+ ‐Ln 3+ doped Cs 2 NaYbCl 6 DPs at different temperatures and relative positions of energy levels of rare earth synergistically determine the physical processes of luminescence. These multi‐mode luminescent materials exhibit good performance in anti‐counterfeiting, NIR imaging, and temperature sensing. This work provides new physical insights into the effects of temperature and energy levels of rare earth on the energy transfer mechanism and related photophysical process.