Cs2NaBiCl6:Mn2+—A New Orange-Red Halide Double Perovskite Phosphor

In this work, we report on the promising photoluminescent behavior of the cubic double perovskite Cs2NaBiCl6 doped with Mn2+ ions. Localized excitations centered on Bi3+ ions in the host lattice strongly absorb near-UV light. In the undoped host compound, only very weak photoluminescence is observed, but in manganese-doped samples, energy transfer from Bi3+ to Mn2+ leads to intense orange-red photoluminescence. A broad emission peak centered at 590 nm is assigned to the 4T1 → 6A1 transition of octahedrally coordinated Mn2+. The excitation spectrum contains peaks at 294 and 354 nm that arise from 6s2 → 6s16p1 excitations of Bi3+ ions. If the chloride ions are partially replaced by bromide ions, the strongest excitation peak red-shifts to 375 nm. The lack of expensive reagents and toxic elements and the ability to tune the excitation and emission spectra through chemical substitution make Cs2NaBiCl6–xBrx:Mn2+ a promising phosphor system.