Temperature-Dependent Photoluminescence from Well-Resolved Excited State Structures in Rare-Earth-Based 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 reports on the optical properties of DPs primarily concentrate on the room temperature state and only exhibit single emission band. Here, we synthesized Cs 2 NaYCl 6 :Sb 3+ , Dy 3+ DPs by a solvothermal method to realize white light emission with photoluminescence (PL) quantum yield as high as 70.7%. The energy-transfer process from self-trapped excitons (STEs) to Dy 3+ ions was revealed by optical characterization and theoretical simulation calculations. Interestingly, we observed the double-emission from low-energy STE emission of Sb 3+ ions and Dy 3+ emission at low temperatures, and the double-emission is consistent with the asymmetric doublet feature of the 3 P 1 → 1 S 0 transition split into two minima. The PL spectra further showed that the fluorescence intensity ratios of Dy 3+ ions at 580 and 680 nm were strongly temperature-dependent, and the relative sensitivity is up to 1.79% K -1 at 360 K. Moreover, the near-infrared and radiation luminescence properties indicated that the Cs 2 NaYCl 6 :Sb 3+ , Dy 3+ DPs also have good prospects for night vision and radiation detection, as well as the great potential for applications in solid-state illumination and optical temperature measurement.