Optoelectronic properties of the two-dimensional ZnO/MoSe₂ heterostructure studied via density functional theory and its application in photocatalytic water splitting

​In this study, the electronic and optical properties of a two‑dimensional van der Waals ZnO/MoSe₂ heterostructure were investigated using first‑principles calculations within the framework of density functional theory (DFT). To obtain a more accurate description of the electronic structure, both the GGA‑PBE approximation and the hybrid exchange–correlation functional HSE06 were employed. The results reveal that the heterostructure exhibits an indirect band‑gap semiconducting nature, with a band‑gap value of 1.26 eV calculated using the HSE06 functional. The projected density of states analysis confirms a type‑II band alignment accompanied by an efficient spatial separation of electrons and holes across the two layers. Charge‑density difference analysis further indicates a net charge transfer from the ZnO layer to MoSe₂, resulting in the development of an internal interfacial electric field that can effectively suppress carrier recombination.Moreover, the influence of biaxial strain within the range of ±4% on the band structure and band‑edge positions was examined. The results show that compressive strain leads to an increase in the band gap, and at approximately −3% strain, an indirect‑to‑direct band‑gap transition occurs. Favorable band‑edge alignment with respect to the redox potentials of water is also preserved under −1% and −3% compressive strain. Optical property calculations reveal a high absorption coefficient in the visible and ultraviolet regions, reaching maxima on the order of 10⁶ cm⁻¹. These findings demonstrate that strain engineering can effectively tune the electronic and optical characteristics of the ZnO/MoSe₂ heterostructure, making it a promising candidate for photocatalytic applications, particularly in water‑splitting processes.