Tunable Band Alignment and Photovoltaic Potential in a Type-II Sb₂S₃/SnSe₂ Heterostructure

Abstract

2D 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, formation mechanism, electronic structure, optical absorption, carrier mobility, and photovoltaic performance of a Sb₂S₃/SnSe₂ heterostructure. The heterostructure is thermodynamically stable and forms a type-II band alignment with an indirect band gap of 1.04 eV, enabling efficient spatial separation of photogenerated carriers. Compared with the isolated monolayers, the heterostructure exhibits enhanced optical absorption in the visible and ultraviolet regions as well as improved carrier mobility, and its power conversion efficiency is estimated to reach 19.74%. 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 alignment, while the optical absorption is weakly affected by the electric field. These results demonstrate the promising potential of the Sb₂S₃/SnSe₂ heterostructure for photovoltaic and optoelectronic applications.