A comparative study of the structural, mechanical, electronic, and optical properties of lead-free cubic AGeX3 (A = Cs, K, and Rb; X = Cl, Br, and I) perovskites: Insights from DFT simulation

Abstract

In this study, a comparative analysis of the structural, mechanical, electronic, and optical properties of cubic perovskites AGeX3 (A = Cs, K, and Rb; X = Cl, Br, and I) has been calculated by the density functional theory. The calculated values of structural parameters such as lattice parameters and unit cell volume of all compounds are in excellent agreement with earlier observations reported in the literature. The values of Poisson's and Pugh's ratios indicate that all compounds exhibit a ductile nature except for CsGeI3, for which the value of Pugh's and Poisson's ratios is shown as brittleness nature. All compounds exhibit an anisotropic nature by calculating the Zener anisotropy index and 3D contour plots also reveal the same nature and CsGeCl3 shows the maximum anisotropy nature. The KGeCl3 compound shows the highest Debye temperatures among the other compounds. Electronic band structures and the study of the density of states provide evidence for the semiconductor behavior of these substances. The I-base compounds show the maximum absorption, conductivity, and loss function than Cl and Br base compounds in the visible region, whereas the Cl group especially CsGeCl3 shows maximum absorption, conductivity, and loss function in the UV zone. A combined analysis suggests that the CsGeCl3 sample would be a promising lead-free candidate for high-performance optoelectronic device application in the UV zone.

Keywords

• Halide perovskites
• Optoelectronic properties
• Density functional theory
• First-principles study