First-Principles Investigation of Stable Lead-Free Halide Perovskite Materials Cssnclxbryi3-X-Y for Solar Cell Applications

Abstract

Perovskite solar cells based on hybrid organic-inorganic lead halide materials have attracted immense interest in recent years due to their enhanced power conversion efficiency. However, the toxic lead element and unstable property of the material limit their applications. With first-principles calculations based on density functional theory, we studied a series of seven existing and three potential lead-free perovskite materials made of cesium, tin, and halogen elements, chlorine (Cl), bromine (Br), and iodine (I). We found that the relative concentrations of the halogen atoms determine the crystal structures and the relative stability of the halide perovskites. Chlorine tends to increase the structural stability while iodine plays the role of reducing the band gaps of the mixed halide perovskites. Both first-principles and empirical calculations suggest that three potential lead-free perovskites, CsSnCl2I, CsSnClI2, and CsSnClBrI, are synthesizable. Considering the stability and the requirement of suitable band gaps, we further identify that, among the ten lead-free halide perovskites, CsSnICl2, CsSnIBr2, CsSnClBrI, CsSnBrI2, CsSnClI2, and CsSnI3 are the appropriate choices for solar cell applications.

Keywords: Halide perovskite materials, Electronic structures and bandgaps, structural stability, Lead-free perovskite solar cells, First-principles calculations