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The height and width of Schottky barrier greatly reduce the electron injection efficiency. In this paper, high electron tunneling probability can be achieved by changing the interlayer distance of heterostructure.

Z-scheme van der Waals heterojunctions are very attractive photocatalysts attributed to their excellent reduction and oxidation abilities.

Designing photocatalysts with suitable band alignment and considerable carrier mobility is extremely important. Here, by means of first-principles calculation, we systematically investigated the structural, photoelectronic, and carrier mobility behavior of the two-dimensional Janus MoSSe/WSSe superlattice. The results show that both armchair-type (A

Based on the first-principles calculation, the electronic structure of HfS2/PtSSe heterojunction is systematically studied. The HfS2/PtSSe heterostructure has an intrinsic type-II band alignment, with holes and electrons located at HfS2 and PtSSe, respectively. The charge distribution is well separated, which can effectively prevent carrier recombination. Compared to the isolated PtSSe and HfS2 monolayers, the light absorption of the HfS2/PtSSe heterojunction in both visible and ultraviolet regions is significantly enhanced. Furthermore, the bandgap of the heterojunction can be tuned linearly by the bi-axial strain. Especially, the heterojunction can switch from type-II to type-III band alignment at compress strain strength of −9%. The variation of the bandgap of the heterojunction is related to the increased hybridization of Hf-5d and Se-4p states under compressed strain. The adjustable bandgap indicates that the HfS2/PtSSe heterojunction is a promising high-performance adjustable optoelectronic nanodevice candidate.

In this paper, the electronic structure and photocatalytic mechanism of arsenene/HfS2 heterojunction with the stable structure are explored systematically based on first-principles calculations. The calculated projected band structure shows that arsenene/HfS2 junction has intrinsic type-II staggered band alignment characteristics, with a bandgap of 0.79 eV, which is much smaller than that of the bandgap on both sides. The small inter-layer bandgap and the built-in electric field induced by the charge transfer at the interface can accelerate the transfer of photo-generated electrons and holes along the Z-scheme path. The appropriate band edge position and efficient charge carriers separation qualify arsenene/HfS2 heterojunction to be an excellent photocatalyst for water splitting. Moreover, the Gibbs free energy diagram indicates that solar energy can effectively drive water splitting on arsenene/HfS2 junction. The influence of the bi-axial strain and pH value of water are discussed. Our calculations predict that the arsenene/HfS2 van der Waals heterojunction can be a promising candidate for direct Z-scheme photocatalyst for overall water splitting.

Both 2D perovskite Cs

ZnSnP2 is a promising photovoltaic absorber material with a direct band gap of 1.68 eV, further reducing the band gap of ZnSnP2 that can achieve higher photovoltaic conversion efficiency. To achieve this target, the influence of biaxial in-plane strain (±3%) on the band gap, hole effective mass and optical properties of ZnSnP2 were investigated by first-principles calculations via Modified Becke–Johnson exchange potential. The results indicate that the biaxial tensile strain can reduce the band gap of ZnSnP2 from 1.3 eV to 1.0 eV and enhance the absorption of visible light of c-axis direction, while the biaxial compress strain increases the band gap of ZnSnP2 slightly. This research provides an alternative approach to tune the band gap of ZnSnP2 by strains. The variation of the band gap under different strains is determined by the highest-energy valance band state, and it can be explained by the redistribution of electrons under different strain.