Unusual Temperature-Dependent Photoluminescence Due to Competing Excited-State Energy Transfer in Rare Earth Double Perovskites

Lead-free halide double perovskites (DPs) have become a research hotspot in the field of photoelectrons due to their unique optical properties and flexible compositional tuning. However, the luminescence of DPs exhibits thermal quenching at high temperatures, which severely affects their further application. Herein, we synthesized the rare earth Dy3+ and transition metal Mn2+ codoped Cs2NaYCl6 rare earth DPs and characterized the optical properties using temperature-dependent photoluminescence spectra and time-resolved photoluminescence decay profiles at different temperatures. The Mn2+-Dy3+:Cs2NaYCl6 DPs exhibit stronger luminescence with increasing temperature, attributed to antithermal quenching. The successful incorporation of Mn dopants in the DPs lattice results in suppression of nonradiative recombination, more efficient energy transfer (ET) to Dy3+, and a reduced lattice distortion. These kinds of DPs with near-infrared luminescence have promising prospects in applications such as night vision, radiation detection, solid-state lighting, and optical temperature measurement.