Van der Waals heterostructure of Janus transition metal dichalcogenides monolayers (WSSe-WX2 (X=S, Se))

A first principles study of a van der Waals heterostructure based on MS2 (M = Mo, W) and Janus CrSSe monolayers

The strategy of stacking two-dimensional materials for designing van der Waals heterostructures has gained tremendous attention in realizing innovative device applications in optoelectronics and renewable energy sources. Here, we performed the first principles calculations of the geometry, optoelectronic and photocatalytic performance of MS2-CrSSe (M = Mo, W) vdW heterostructures. The mirror asymmetry in the Janus CrSSe system allows the designing of two models of the MS2-CrSSe system by replacing S/Se atoms at opposite surfaces in CrSSe. The feasible configurations of both models of the MS2-CrSSe system are found energetically, dynamically and thermally stable. The studied heterobilayers possess an indirect type-I band alignment, indicating that the recombination of photogenerated electrons and holes in the CrSSe monolayer is hence crucial for photodetectors and laser applications. Remarkably, a red-shift in the optical absorption spectra of MS2-CrSSe makes them potential candidates for light harvesting applications. More interestingly, all heterobilayers (except W(Mo)S2-CrSSe of model-I(II)) reveal appropriate band edge positions of the oxidation and reduction potentials of the photocatalysis of water dissociation into H+/H2 and O2/H2O at pH = 0. These results shed light on the practical design of the MS2-CrSSe system for efficient optoelectronic and photocatalytic water splitting applications.

Janus transition metal dichalcogenides in combination with MoS2 for high-efficiency photovoltaic applications: a DFT study

Exotic features of two-dimensional materials have been demonstrated, making them particularly appealing for both photocatalytic and photovoltaic applications. van der Waals corrected density functional theory calculations were performed on AAII-Se MoSSe, AAII-Te MoSTe, and AAII-Se WSSe heterostructures in this study. Our findings reveal that the heterostructures have high stability due to the tiny lattice mismatch and binding energy, which is extremely favorable for epitaxial growth of these heterostructures. According to the electronic band gap calculation, AAII-Se MoSSe and AAII-Se WSSe are semiconducting materials, while AAII-Te MoSTe has metallic properties. Interestingly, all three heterostructures have type II band gap alignment, which is advantageous for photovoltaic and photocatalytic applications. Furthermore, it was discovered that AAII-Se MoSSe and AAII-Se WSSe heterostructures exhibit high power conversion efficiency of up to 12.15% and 9.37%, respectively. Based on these intriguing features, the two heterostructures are excellent prospects for photovoltaic applications. The heterostructures have no appropriate band edge sites for overall water splitting at pH = 0, but they are good for the oxygen evolution process. It is feasible to alter the position of the band edges using strain resulting in improved overall water splitting by the heterostructures.