Direct Electron Transfer Enables Highly Efficient Dual Emission Modes of Mn<sup>2+</sup>-Doped Cs<sub>2</sub>Na<sub>1–<i>x</i></sub>Ag<sub><i>x</i></sub>BiCl<sub>6</sub> Double Perovskites
Min Wang, Jing Lyu, Xian Qin, Shuo‐Wang Yang, Xiaogang Liu, Guo Qin Xu
Abstract
Double perovskites with bright emission, low toxicity, and excellent stability have drawn considerable attention. Herein, we report the hydrothermal synthesis of Mn2+-doped Cs2Na1–xAgxBiCl6 double perovskites that exhibit dual emission modes. Introducing Ag+ ions to Cs2NaBiCl6 samples enables a bright self-trapped exciton (STE) emission in orange-red color, whereas Mn2+ dopants induce a yellow-orange emission. Importantly, Mn2+ doping into Cs2Na1–xAgxBiCl6 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 Cs2NaBiCl6 can localize wave function to the [AgCl6]5– octahedron and convert dark transitions to bright STE transitions. Moreover, the 3d orbitals of Mn2+ dopants hybridize with Bi-6p and Cl-3p orbitals at the conduction band minimum, resulting in direct electron transfer from the host to Mn2+ and a significant increase in photoluminescence efficiency. These results shed light on the optical physical process of Mn2+-doped systems, providing useful information for further improvement of the photoluminescence efficiency of double perovskites.