Journal of Inorganic Materials ›› 2022, Vol. 37 ›› Issue (6): 691-696.DOI: 10.15541/jim20210491

Special Issue: 【虚拟专辑】计算材料 【能源环境】钙钛矿

• RESEARCH LETTER • Previous Articles    

Stability of Low-index Surfaces of Cs2SnI6 Studied by First-principles Calculations

LIN Aming1,2(), SUN Yiyang1,2()   

  1. 1. Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2021-08-05 Revised:2021-08-20 Published:2022-06-20 Online:2021-11-01
  • Contact: SUN Yiyang, professor. E-mail: yysun@mail.sic.ac.cn
  • About author:LIN Aming (1996–), female, Master candidate. E-mail: linaming@student.sic.ac.cn
  • Supported by:
    Shanghai International Cooperation Project(20520760900)

Abstract:

Cs2SnI6 is a stable and environmentally friendly halide perovskite material with great potential for photovoltaic and optoelectronic applications. While the surface properties are of paramount importance for device fabrications, there have been no such theoretical studies on this material. Using density functional theory calculations with the SCAN+rVV10 functional, the (001), (011) and (111) surfaces of Cs2SnI6 were studied to reveal their thermodynamic stability. We constructed seven models for these surfaces, including two along the (001) orientation (CsI2- and SnI4-terminated surfaces), two along the (011) orientation (I4- and Cs2SnI2-terminated surfaces) and three along the (111) orientation (non-stoichiometric CsI3-, Sn- and stoichiometric CsI3-terminated surfaces). Because most of the surfaces are non-stoichiometric, their relative stability depends on the experimental preparation condition, which is reflected by the chemical potentials of the constituent elements in the calculation. By determining the allowed chemical potential region, the thermodynamic stability of these Cs2SnI6 surfaces is analyzed. The results show that the surface energies of the (001) and (011) surfaces are affected by the chemical potentials, while the stoichiometric CsI3-terminated (111) surface is unaffected by the chemical potentials and is energetically the most stable surface of Cs2SnI6. Thus, the observed exposure of (111) surface of Cs2SnI6 crystals in several recent experiments is determined to be driven by thermodynamics.

Key words: perovskite, surface energy, Cs2SnI6, photovoltaic material, luminescent material

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