Structural and Optoelectronic Properties of Two-Dimensional Ruddlesden–Popper Hybrid Perovskite CsSnBr₃

• Main Authors: Guangbiao Xiang, Yanwen Wu, Yushuang Li, Chen Cheng, Jiancai Leng, Hong Ma
• Format: Article
• Language: English
• Published: MDPI AG 2021-08-01
• Series: Nanomaterials
• Subjects: 2D Ruddlesden–Popper hybrid perovskites; first-principles study; band structures; optoelectronic properties
• Online Access: https://www.mdpi.com/2079-4991/11/8/2119

Ultrathin inorganic halogenated perovskites have attracted attention owing to their excellent photoelectric properties. In this work, we designed two types of Ruddlesden–Popper hybrid perovskites, Cs<i>_n</i>₊₁Sn<i>_n</i>Br_3<i>n</i>+1 and Cs<i>_n</i>Sn<i>_n</i>₊₁Br_3<i>n</i>+2, and studied their band structures and band gaps as a function of the number of layers (<i>n</i> = 1–5). The calculation results show that Cs<i>_n+</i>₁Sn<i>_n</i>Br_3<i>n</i>+1 has a direct bandgap while the bandgap of Cs<i>_n</i>Sn<i>_n</i>₊₁Br_3<i>n</i>+2 can be altered from indirect to direct, induced by the 5<i>p</i>-Sn state. As the layers increased from 1 to 5, the bandgap energies of Cs<i>_n</i>₊₁Sn<i>_n</i>Br_3<i>n</i>+1 and Cs<i>_n</i>Sn<i>_n</i>₊₁Br_3<i>n</i>+2 decreased from 1.209 to 0.797 eV and 1.310 to 1.013 eV, respectively. In addition, the optical absorption of Cs<i>_n</i>₊₁Sn<i>_n</i>Br_3<i>n</i>+1 and Cs<i>_n</i>Sn<i>_n</i>₊₁Br_3<i>n</i>+2 was blue-shifted as the structure changed from bulk to nanolayer. Compared with that of Cs<i>_n+</i>₁Sn_nBr_3<i>n+</i>1, the optical absorption of Cs<i>_n</i>Sn<i>_n</i>₊₁Br_3<i>n</i>+2 was sensitive to the layers along the <i>z</i> direction, which exhibited anisotropy induced by the SnBr₂-terminated surface.