Temperature-dependent self-trapped models regulating energy transfer in rare earth double perovskites via 5s2 electron doping

Abstract

Due to their environmental friendliness, structural plasticity, and tunable emission, lead-free halide double perovskites offer a broad spectrum of applications in light-emitting diode (LED), photodetectors, infrared imaging, and temperature sensing. Herein, we synthesized rare earth-based Cs₂NaYCl₆ double perovskites using a solvothermal method, and Sb³⁺/Sm³⁺ co-doping can effectively modulate the luminescence by adjusting the band gap structure and channels of energy transfer. With the Sm³⁺-feeding concentration increasing, the emission could be adjusted from blue to white, attributed to an effective energy transfer from the self-trapped state to Sm³⁺. Temperature-dependent photoluminescence spectra indicate that the double self-trapped exciton emission at low temperatures originated from two minima in the excited state of ³P₁. The relative sensitivity of the optical temperature sensor reached 1.08% K⁻¹, which was better than that of other rare earth perovskites. The LED device based on Sb³⁺/Sm³⁺ co-doped Cs₂NaYCl₆@polymethylmethacrylate displays a chromaticity coordinate of (0.29, 0.28), a color rendering index of 87, and the correlated color temperature of 10 986 K. Our work explores an in-depth understanding of energy transfer in double self-trapped states and provides new material for advanced applications.