Competing Energy Transfer-Modulated Dual Emission in Mn 2+ -Doped Cs 2 NaTbCl 6 Rare-Earth Double Perovskites.

A 2 B I B III X 6 double perovskites are promising materials due to their outstanding photoelectronic properties and excellent stability in the environment. Herein, we synthesized Mn 2+ :Cs 2 NaTbCl 6 with dual emission through a solvothermal method for the first time. Mn 2+ :Cs 2 NaTbCl 6 double perovskites exhibit excellent environmental stability and high photoluminescence quantum yields (PLQYs). The Cs 2 NaTbCl 6 was successfully doped with Mn 2+ in two modes: at Mn-feeding concentrations below 1%, Mn 2+ first tend to insert into the interstitial void, but if the Mn-feeding concentration exceeds 1%, Mn 2+ will further substitute Na + site of the Cs 2 NaTbCl 6 lattice and thus both two doping modes coexist. After Mn 2+ doping, efficient energy transfer from the 5 D 4 level of Tb 3+ ions to the 4 T 1 level of Mn 2+ ions occurs, resulting in tunable dual emission from the Tb 3+5 D 4 → 7 F J=6,5,4,3 transition and Mn 2+4 T 1 → 6 A 1 transition. Further, LED based on the Mn 2+ :Cs 2 NaTbCl 6 double perovskites exhibits excellent performance and stability. This work demonstrates a strategy to achieve novel lanthanide-based double perovskites with potential applications in photonics.