Physical characteristics of Cs2XTlCl6(X = Sc, Y) double perovskites for energy harvesting applications

Abstract

To compute the structural, electronic, optical, elastic, and thermoelectric (TE) characteristics of Cs2ScTlCl6 and Cs2YTlCl6 halide double perovskites, the first principles method is employed by using density functional theory (DFT) based full potential linearized augmented plane wave (FP-LAPW) scheme. Band structure (BS) and density of states (DOS) revealed the direct band gap (Eg) of 4.44/5.22 eV for Cs2ScTlCl6/Cs2YTlCl6, correspondingly. To explore the thermodynamic and structural stability of the Cs2ScTlCl6 and Cs2YTlCl6, the formation enthalpy (ΔH) and tolerance factor (τ) are computed. The optical absorption edges are located at 3.8 for Cs2ScTlCl6 and 5.1 eV for Cs2YTlCl6. The distinct absorption characteristics observed, particularly in the UV spectrum, suggest that both materials hold promise for use in advanced optoelectronic devices. Elastic constants for both compounds are predicted to determine mechanical features. The Poisson's ratio and Cauchy pressure (CP) depicted brittle nature of both perovskites. Furthermore, BoltzTraP program is utilized to examine TE features and the analysis of ZT spectrum reveals an increase in ZT, rising from 0.747 to 0.800 for Cs2ScTlCl6 and from 0.740 to 0.802 for Cs2YTlCl6, as temperatures increase from 300 to 800 K. TE materials, with enhanced ZT values, hold promise for diverse applications, including efficient power generation, wearable technology, automotive systems, space exploration, and industrial processes.