Pressure-dependent comparative study of the mechanical, electronic, and optical properties of CsPbX3 (X = Cl, Br, I): a DFT study for optoelectronic applications

Abstract

Inorganic metal-halide perovskite (MHP) materials are potential candidates for optoelectronic and energy-storage device applications. In this work, a systematic hydrostatic pressure-dependent investigation of the elastic, electronic, optical, and photocatalytic properties of CsPbX₃ (X = Cl, Br and I) was performed based on ab initio simulations. This study revealed that the mechanical stability of Cl- and Br-containing perovskites could be sustained up to 20 and 25 GPa, respectively, while CsPbI₃ could survive up to 75 GPa applied pressure. It was also found that the mechanical properties of CsPbX₃ perovskites were ductile under ambient conditions and their ductility significantly improved (decreased) with pressure. The electronic property calculations suggested that CsPbX₃ perovskites have a direct energy band gap, which decreases with increasing pressure due to structural change and/or a shifting of the conduction band minimum toward the Fermi level. The band gap became zero under pressures of 20.0, 15.0, and 10.0 GPa for Cl-, Br-, and I-based halides, indicating the transition of the crystal structure. The absorption peak of CsPbX₃ perovskites radically shifted toward the low photon energy region with applied pressure. The photoconductivity, reflectivity, and dielectric constant showed an increasing tendency under pressure. These findings would be beneficial for experimental study and suggest that pressure has significant effect on the physical properties of CsPbX₃ perovskites, which might be a promising avenue for exploitation in optoelectronic and photonic applications.