DFT study of X‐site ion substitution doping of Cs2PtX6 on its structural and electronic properties.

Summary: The stability and toxicity of perovskite solar cells are still preventing full industrialization. Therefore, lead‐free all‐inorganic double perovskite materials have become the focus of research in recent years. Our group proposed a new narrow bandgap lead‐free double perovskite solar cell using a high‐quality Cs2PtI6 film. In this paper, for the purpose of exploring the trend in the bandgap and stability of the perovskite‐derived Cs2PtI6 substituted by halogen ions, we performed a first‐principles investigation based on density functional theory to study the structural and electronic properties of Cs2PtI6−yCly, Cs2PtI6−yBry, Cs2PtBr6−yCly (y = 0, 1, 2, 3, 4, 5, 6). The calculated structural parameters revealed a good mechanical stability for all these compounds, and the trend in the formation energy indicated that the substitution of I− with Cl− and Br− can significantly reduce the energy and improve the thermodynamic stability. Through a comparative analysis of the electronic properties of Cs2PtX6 (X = Cl, Br, I), we found that the substitutional doping of halogen ions can effectively adjust the bandgap and show an obvious change trend. The present study may demonstrate an effective theoretical guidance for preparing lead‐free all‐inorganic perovskite solar cell materials with appropriate bandgap and excellent stability. [ABSTRACT FROM AUTHOR]