Tunable band alignment and photovoltaic potential in a type-II Sb2S3/SnSe2 heterostructure

Abstract

2D van der Waals (vdW) heterostructures offer an effective route for designing high-performance optoelectronic and photovoltaic devices through interfacial band engineering. Here, based on first-principles calculations, we systematically investigate the structural stability, electronic structure, optical absorption, carrier mobility, and photovoltaic performance of a Sb₂S₃/SnSe₂ heterostructure. The heterostructure is thermodynamically stable and exhibits a type-II band alignment with an indirect band gap of 1.04 eV, where the conduction band minimum (CBM) is mainly contributed by SnSe₂ and the valence band maximum (VBM) is dominated by Sb₂S₃. This band alignment enables efficient spatial separation of photogenerated carriers. Compared with the isolated monolayers, the heterostructure exhibits enhanced optical absorption in the visible and ultraviolet regions, together with high and anisotropic carrier mobility, with the maximum electron and hole mobilities reaching 5.31 × 10⁴ and 5.82 × 10⁴ cm² V⁻¹ s⁻¹, respectively. Furthermore, the predicted power conversion efficiency reaches 19.74%, indicating excellent photovoltaic performance. Moreover, the electronic structure can be effectively tuned by in-plane strain and external electric fields, inducing a transition between type-I and type-II band alignments, while the optical absorption is only weakly affected by the electric field. These results demonstrate the promising potential of the Sb₂S₃/SnSe₂ heterostructure for next-generation photovoltaic and optoelectronic applications.