A theoretical investigation on optoelectronic and photocatalytic behaviour of Janus X-Ga-Al-Y (X, Y--S and Te) monolayers

The structural, electronic, and optical characteristics of hexagonal Janus X-Ga-Al-Y (X, Y--S and Te) monolayers have been assessed within the theoretical framework by using density functional theory. The negative cohesive energy of all monolayers confirms the energetic stability. The phonon dispersion diagram validates that all Janus X-Ga-Al-Y (X, Y--S and Te) monolayers are dynamically stable. The obtained indirect type band gap values of monolayers GaS, GaAlS2, GaAlTe2, SGaAlTe, and TeGaAlS are 3.25 eV, 2.87 eV, 2.45 eV, 2.25 eV, and 1.39 eV by utilizing Heyd-Scuseria-Ernzerhof functional respectively which indicates their semiconductor behaviour. All the monolayers possess the utmost absorption in the ultraviolet (UV) portion. Hence, X-Ga-Al-Y (X, Y--S and Te) monolayers have promising applications as UV absorbers, optoelectronic devices, and UV detectors. The band edge alignments of the X-Ga-Al-Y (X, Y--S and Te) monolayers also have been analyzed which suggests that X -Ga-Al-Y (X, Y--S and Te) monolayers are efficient as photocatalysts for hydrogen production.