Halide perovskites have gained attention as promising materials over the past decade, where high energy conversion efficiency is key for thermoelectric and solar applications. However, challenges remain: organic cations in halide perovskites are unstable, and the presence of lead raises concerns about toxicity. To address and reduce these issues, we examine the thermodynamic stabilities and the thermoelectric, mechanical, and optical properties of X2TlAgCl6 (X = K, Rb, Cs) perovskites. The main objective is to evaluate the potential use in renewable energy and optoelectronic devices. The cubic stability of the anticipated series of materials was validated using the new tolerance factor, octahedral factor, and Goldsmith tolerance factor. Furthermore, to verify their dynamic stability, we evaluated their formation energy, phonon dispersion, and Gibbs free energy and performed an AIMD study. We employed the TB-mBJ, TB-mBJ-SOC, and HSE06 functionals to predict electronic properties accurately. The analysis of the band profile revealed that the studied perovskites are direct (Г-Г) band gap semi conducts with band gap values of 0.91/0.89/0.27 eV for K2TlAgCl6, 0.89/0.87/0.23 eV for Rb2TlAgCl6, and 0.86/0.76/0.21 eV for Cs2TlAgCl6, as calculated with TB-mBJ/TB-mBJ-SOC/HSE06. Following TB-mBJ functionalization, the investigated compounds exhibit remarkable optical properties, with elevated light absorption coefficients (104 cm− 1) and low reflectivity across the near-infrared to visible spectrum, rendering them suitable for use in low-frequency detectors, optoelectronic devices, and solar cells. Mechanical stability was validated using Born–Huang criteria, based on their stiffness constants. The ductility of perovskites is substantiated by Cauchy pressure, Poisson’s ratio, and Pugh’s ratio. The material exhibits semiconductor behavior with holes as the majority carriers, with a maximum thermal conductivity of 6.614 W/mKs at high temperatures. At room temperature, the power factor reaches 2.8 × 1011 W/mK2s, confirming a strong thermoelectric potential.
Shah et al. (Tue,) studied this question.