First-principles calculations to investigate structural, mechanical, electronic, optical, and thermoelectric properties of novel cubic double Perovskites X2AgBiBr6 (X=Li, Na, K, Rb, Cs) for optoelectronic devices

ABSTRACT

Structural, elastic, electronic, optical, and thermoelectric properties of cubic double perovskites X₂AgBiBr₆ (X = Li, Na, K, Rb, Cs) were investigated using the density functional theory (DFT) method. The DFT calculations were carried out with various exchange-correlation potentials, e.g. LDA, GGA-PBE, GGA-WC, and hybrid functionals (YS-PBE0). Structural and elastic properties of X₂AgBiBr₆ demonstrate that these compounds are ionically bonded, elastically stable, ductile, and anisotropic. Calculations show that the compounds are semiconductors with indirect bandgap at the (X- L) point, with bandgap values of 2.124, 2.222, 2.198, 2.209, and 1.902 eV for X₂AgBiBr₆ (X = Li, Na, K, Rb, and Cs), respectively. Due to their distinguishing optical characteristics and indirect wide bandgap, these compounds might be utilised as absorber layers in solar cells and other optoelectronic devices. Moreover, thermoelectric properties show that the Figure of Merit (ZT) has values of 0.713, 0.723, 0.721, 0.726, and 0.728 for X₂AgBiBr₆ (X = Li, Na, K, Rb, Cs). The Figure of Merit shows a plateau in the temperature range of 500–900 K, which corresponds to the highest value of ZT. All investigated compounds have holes as the majority of charge carriers. Thermoelectric properties of X₂AgBiBr₆ compounds reveal that these compounds can be employed in thermoelectric devices.

KEYWORDS:

• Double perovskite
• DFT
• full hybrid functional
• solar cell
• optical and thermo-electronic conductivities

Acknowledgment

The financial support from The Hashemite University is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).