Cs4Cd1-xMnxBi2Cl12-A Vacancy-Ordered Halide Perovskite Phosphor with High-Efficiency Orange-Red Emission

The structural, optical, and magnetic properties of the vacancy-ordered quadruple perovskites Cs4CdBi2Cl12 and Cs4MnBi2Cl12 and their solid solution have been investigated. Both compounds crystallize with the R3m space group symmetry that arises from the ordering of Bi3+, Mn2+/Cd2+, and cation vacancies into layers that run perpendicular to the < 111 > direction of the cubic perovskite structure. Cs4MnBi2Cl12 is paramagnetic down to 2 K with a Weiss constant of -2.88(3) K and an effective moment of 5.840(1) mu(B). This compound exhibits weak orange-red luminescence, which involves Bi3+ ions absorbing near-UV photons, followed by energy transfer to Mn2+ ions and finally radiative decay that is attributed to a spin-forbidden T-4(1) (G) -> (6)A(1) (S) d-d transition. The emission peak is centered near 605 nm with a fullwidth at half-maximum of similar to 90 nm and a photoluminescence quantum yield (PLQY) of similar to 4%. The isostructural Cs4CdBi2Cl12 is neither magnetic nor does it show detectable PL at room temperature. Replacing Mn2+ with Cd2+ to form Cs4Cd1-xMnxBi2Cl12 leads to a zero-dimensional electronic structure that inhibits energy migration to defect sites where nonradiative decay can occur, increasing the room temperature PLQY to 57% in the x = 0.27 sample. Cs4Cd1-xMnxBi2Cl12 phosphors are easily synthesized from solution, do not contain rare-earth ions, and possess emission spectra that compare favorably to narrow band, red phosphors containing Eu2+.