First-principles investigation of structural, electronic, optical, elastic, and thermal properties of double perovskites Cs2AgMX6 (M = Al, In, Ga; X = Br, Cl) for thermoelectric and water splitting applications

초록

In this work, we explore the structural, electronic, optical, thermoelectric, photocatalytic, elastic and thermal properties of halide double perovskites, Cs2AgMX6 (M = Al, Ga, and In, X = Cl and Br) using density functional theory (DFT) and semi-classical Boltzmann transport theory. Electronic calculations reveal direct band gap for all compounds. The lowest and highest band gap is observed 2.03 eV and 3.84 eV for Cs2AgGaBr6 and Cs2AgAlCl6, respectively. All bandgap values are in good agreement with other theoretical work. Optical properties show high absorption in Ultra Violet region for all compounds. Thermodynamic properties shows the better stability of these compound due to high Debye temperature (theta D), especially for Cs2AgGaCl6. while all materials are elastically stable except for Cs2AgGaCl6, by analyzing mechanical properties. In addition to that, all materials exhibit remarkable thermoelectric (TE) properties, with the highest Seebeck coefficient recorded for Cs2AgGaCl6 at room temperature being 188 mu V/K and lowest kappa L of 1.01 W/mK, which results in highest ZT of 0.752 at 450 K and makes it potential candidate for TE applications. In addition to that, all materials exhibit remarkable thermoelectric properties as well as photocatalytic for water splitting applications.

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