Janus XMPYS (X=Se, Te; M=Mo, W; YAl, Ga) monolayers with enhanced spintronic properties and boosted solar-to-hydrogen efficiency for photocatalytic water splitting

In this article, we investigate the potential feasibility of new Janus XMPYS (X = Se, Te; M = Mo, W; YAl, Ga) monolayers using first-principles calculations. All eight studied monolayers are shown to be direct semiconductors with moderate bandgaps ranging from 1.30 eV to 1.47 eV. The asymmetric structure of Janus XMPYS together with the presence of heavy transition metals (M = Mo, W) results in the considerable valley and Rashba spin-splittings desirable for valleytronic and spintronic applications. It is also shown that strain can be used to modulate the spin-related properties of the proposed structures. Among XMPYS monolayers, the four with X = Se meet the band alignment requisite for overall water splitting. Moreover, these monolayers are predicted to have excellent solar-to-hydrogen efficiency of 25.61%–28.08%. Excitingly, it is found that by applying tensile strain an impressive efficiency of 39% can be achieved in SeWPAlS and SeWPGaS monolayers.