Direct Electron Transfer Enables Highly Efficient Dual Emission Modes of Mn-Doped CsNaAgBiCl Double Perovskites.

Double perovskites with bright emission, low toxicity, and excellent stability have drawn considerable attention. Herein, we report the hydrothermal synthesis of Mn-doped CsNaAgBiCl double perovskites that exhibit dual emission modes. Introducing Ag ions to CsNaBiCl samples enables a bright self-trapped exciton (STE) emission in orange-red color, whereas Mn dopants induce a yellow-orange emission. Importantly, Mn doping into CsNaAgBiCl double perovskites with an indirect bandgap enables a high photoluminescence quantum yield of 49.52 ± 2%. Density functional theory calculations reveal that bringing Ag ions into CsNaBiCl can localize wave function to the [AgCl] octahedron and convert dark transitions to bright STE transitions. Moreover, the 3d orbitals of Mn dopants hybridize with Bi-6p and Cl-3p orbitals at the conduction band minimum, resulting in direct electron transfer from the host to Mn and a significant increase in photoluminescence efficiency. These results shed light on the optical physical process of Mn-doped systems, providing useful information for further improvement of the photoluminescence efficiency of double perovskites.