Structural, optoelectronic and thermoelectric properties of the new perovskites LiMCl₃ (M = Pb or Sn): a DFT study

In this manuscript, structural, electronic, optical and thermoelectric properties of chloride perovskites LiMCl₃ (M = Pb or Sn) have been studied using Density Functional Theory (DFT) implemented in ABINIT code. The exchange–correlation functionals is treated with Generalized Gradient Approximation of Perdew Burke Ernzerhof (GGA-PBE). Structural properties revealed that the equilibrium lattice parameters for LiPbCl₃ and LiSnCl₃ are 5.686 and 5.597 Å respectively. These values were used to investigate the thermodynamic stability of these materials by evaluating the energy of formation. The negative formation energy results suggest that the synthesis of LiPbCl₃ and LiSnCl₃ perovskites is feasible. Further, electronic properties revealed that LiMCl₃ (M = Pb and Sn) perovskites are semiconductors with indirect band gaps of 1.87 and 0.98 eV for LiPbCl₃ and LiSnCl₃, respectively. From the optical properties, we found that the studied materials have a high absorption coefficient, greater than 10⁴ cm⁻¹ in the visible region, indicating their suitability as photovoltaic absorber materials. The results of the elastic properties show that both perovskites are stable and possess ductile behavior. In addition, thermoelectric properties of LiMCl₃ (M = Pb and Sn) have been calculated and analyzed using the combination of electronic structure and Boltzmann transport theory. The thermoelectric efficiency results suggest that LiPbCl₃ and LiSnCl₃ could be potential candidates for thermoelectric devices for high-temperature applications.