Optoelectronic and transport response of double perovskites Na2AuMX6 (M = Al, Ga, and X = Br, I) for energy harvesting: A DFT investigation

Abstract

In the current article, the structural configuration, elastic behaviour, optoelectronic response, as well as thermoelectric features of the novel double perovskites Na₂AuMX₆ (M = Al, Ga, and X  = Br, I) have been thoroughly investigated. The stability in the cubic phase of Na₂AuAlBr₆, Na₂AuAlI₆, Na₂AuGaBr₆, and Na₂AuGaI₆ has been verified by tolerance factor prediction. The elastic factors have proposed the mechanical stability, ductility, and anisotropic response of the investigated compounds. The electronic attributes computations verified the existence of a direct band gap (E_g). The compounds Na₂AuAlBr₆, Na₂AuAlI₆, Na₂AuGaBr₆, and Na₂AuGaI₆ have an E_g of 1.82 eV, 0.45 eV, 1.53 eV, and 0.22 eV, respectively. This study further specifically emphasizes the screening of photon absorption, polarizability, refraction of light, reflection, and loss factor. The optical characteristics of Na₂AuAlBr₆ and Na₂AuGaBr₆ are suitable for solar cells due to the visible light absorption features. Meanwhile, the optical aspects of Na₂AuAlI₆ and Na₂AuGaI₆ are compatible with optoelectronic applications due to infrared absorption of light. The thermoelectric features are obtained using the BoltzTraP code, which showed that the highest ZT values are ascertained to be 0.79, 0.76, 0.71, and 0.76, respectively, for the studied materials. Based on this analysis, these materials have provided theoretical evidence and future recommendations for implications in solar cells, optoelectronics, and thermoelectric technologies.