Structural, Electronic, and Optical Properties of Cs2SnX4 (X = Cl, Br, and I) Multilayers: A Density Functional Theory Study

The Cs 2 SnX 4 (X = Cl, Br, and I) halide perovskites are currently emerging as a new family of 2D materials and promising candidates for photovoltaic and optoelectronic devices. Herein, the structural, electronic, and optical properties of the Cs 2 SnX 4 multilayers (Ms) with 1–3 layers are investigated by density functional theory (DFT). The structural properties show that the bond length variation of Cs 2 SnX 4 is closely related to surface effects. The Cs 2 SnCl 4 Ms have the lowest formation energies and the best stability, and the formation energies decrease and the stability improves when the number of layers increases. The electronic properties show that the direct‐bandgap semiconductor Cs 2 SnX 4 Ms bandgap values (Cl: 1.513–1.188–0.932, Br: 1.342–1.015–0.862, I: 1.198–0.903–0.729) decrease with the change from 1 to 3 layers and from Cl to I. The p orbitals of X atoms and 5 p orbitals of Sn atoms are mainly involved in conduction. The optical properties indicate that Cs 2 SnX 4 Ms achieve coverage and adjustability in the near‐infrared and visible‐light ranges. The calculations provide a fundamental theoretical basis for the research and application of Cs 2 SnX 4 .