Lead-free perovskites InSnX3 (X = Cl, Br, I) for solar cell applications: a DFT study on the mechanical, optoelectronic, and thermoelectric properties

Abstract

This study aims to explore for the first time the mechanical, electronic, optical and thermoelectric properties of cubic lead-free perovskites InSnBr _3 and InSnI _3 to investigate their potential applications in solar cell devices. Additionally, the previously examined InSnCl _3 perovskite is also included. The properties of the perovskites were determined using first-principles calculation based on the well-known Density Functional Theory (DFT) with the Generalized Gradient Approximation (GGA) functional implemented in the Quantum Espresso package. One of the most important findings was that the bandgaps of the compounds decrease and undergo an indirect-to-direct bandgap transition when Cl is replaced by Br and I. This indicates that InSnBr _3 and InSnI _3 perovskites are more suitable for solar cell applications. The bandgap energies for InSnCl _3 , InSnBr _3 , and InSnI _3 perovskites are 0.59 eV (R→X), 0.44 eV (R→R), and 0.24 eV (R→R), respectively. The improved band gaps using the HSE06 functional are 2.35 eV, 2.13 eV, and 2.01 eV for the respective perovskites. The materials were found to possess chemical, mechanical, and thermodynamic stability as well as ductile behaviour. Furthermore, the materials exhibit remarkable optical properties, including high absorption coefficients and relatively small reflectivity. The calculated thermoelectric properties indicated high electrical conductivity and reasonable figure of merit values, making them promising candidates for the application in thermoelectric devices.

Keywords

• density functional theory
• quantum espresso
• InSnX3 perovskites
• optoelectronic properties
• mechanical properties
• thermoelectric properties