Luminescence Mechanism of <i>ns</i><sup>2</sup> Ions in Cs<sub>2</sub>(Sn/Hf)Cl<sub>6</sub> Revealed by First-Principles Calculations
Ruijie Hao, Mingzhe Liu, Min Yin, Chang‐Kui Duan
Abstract
A great variety of halide perovskites doped with ns 2 ions have been explored for optical functional materials, and a couple of different phenomenological models have been proposed to interpret their luminescence. First-principles calculations are carried out for Cs 2 SnCl 6 and Cs 2 HfCl 6 to explore self-trapped excitons, potentially important intrinsic and extrinsic defects, and different defect-related luminescent centers. A uniform picture of competing processes consistent with a previous study on Cs 2 ZrCl 6 is obtained to interpret the experimental phenomena. Remarkable differences in details between Cs 2 SnCl 6 and Cs 2 (Hf/Zr)Cl 6 are also revealed: the high-symmetry self-trapped exciton not stable in Cs 2 (Hf/Zr)Cl 6 is predicted to be stable in Cs 2 SnCl 6, and the activation energy of the high-symmetry Sb 3+ at the M site of Cs 2 M Cl 6 is much smaller for M = Sn than Hf/Zr. The elucidation of the defects and transition mechanisms with first-principles calculations will benefit the design and optimization of metal halide perovskites with ns 2 ion doping.