In recent years, ferroelectric materials capable of reversible self-polarization have garnered considerable interest due to their potential for pioneering advancements in non-volatile memory and adaptive electronic devices. The vertically stacked In2Se3/SnSe2 van der Waals (vdW) heterostructures composed of ferroelectric In2Se3 and InSe2 were constructed, as elucidated by first-principles calculations within the density functional theory (DFT). The results show that two heterostructures exhibit type-II band alignments, which are favorable for photocatalytic devices for separating photogenerated electrons and holes. Crucially, the AA stacking heterostructure stabilizes as an indirect semiconductor with a band gap of 1.42 eV and the AA’ stacking is an indirect semiconductor with band gap of 0.21 eV depending on the polarization direction of In2Se3. The electronic structure of AA stacking heterostructure demonstrates pronounced tunability under external biaxial strain. Moderate compressive or tensile strain can systematically modulate the band gap value and more significantly, can potentially alter the band offset strength between the layers. This strain-dependent control directly influences the spatial overlap of wavefunctions and the intensity of the internal field governing carrier separation, offering a powerful post-synthesis knob for property engineering. Moreover, the interfacial coupling in the heterostructure leads to a remarkable enhancement of optical absorption across the visible spectrum compared to the constituent In2Se3 and SnSe2 monolayers. This enhancement is attributed to new optical transition pathways enabled by the hybridized electronic states at the interface. The synergistic combination of a tunable type-II band alignment, strong visible-light response, and efficient inherent charge separation mechanism establishes the In2Se3/SnSe2 heterostructure as a highly promising material system for applications in visible-light photocatalysis and novel optoelectronic devices.
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