Multimode luminescence and highly anti-thermal quenching in Sb3+/Yb3+/Pr3+ Co-doped Cs2NaYCl6 double perovskites

Abstract

Double perovskites have become a research hotspot in the field of optoelectronic materials due to their environmental friendliness and structural tunability. However, double perovskites with multimode luminescence and thermal stability are still urgently desired for multifunctional fluorescence applications. In this study, yttrium-based double perovskites (Cs₂NaYCl₆) were successfully synthesized by a solvothermal method. The introduction of Yb³⁺ and Pr³⁺ ions enables down-shifting luminescence modulation as well as the extension of the luminescence range under 340 nm excitation, and bright up-conversion luminescence is observed under 980 nm near-infrared laser excitation. Interestingly, both the down-shifting emission of Yb³⁺ ions and the up-conversion emission of Pr³⁺ ions show excellent anti-thermal quenching behavior with increasing temperature, which may be attributed to the fact that the inner 4f electrons of lanthanide ions are less affected by temperature. In particular, the relative sensitivity of an optical temperature sensor based on the fluorescence intensity ratio is as high as 6.72% K⁻¹, which could be the highest value reported. Double perovskites combining multimode emission with anti-thermal quenching provide new materials for advanced applications.