Enhanced optoelectronic performance of MoSi2P4 and SnS2 van der Waals heterojunctions for efficient solar energy harvesting.

This study systematically investigates the potential of the two-dimensional (2D) van der Waals heterostructure (vdWH) MoSi2P4/SnS2 for photovoltaic applications. The heterostructure is composed of two monolayers with a lattice mismatch of 6.42%. Among four constructed stacking configurations, the A4 configuration with the lowest binding energy is selected based on binding-energy calculations. This structure exhibits no imaginary phonon frequencies across the entire Brillouin zone, and AIMD simulations confirm its good thermal stability. It also offers synthetic flexibility and tunable properties, making it suitable for advanced functional devices. Band structure calculations using the HSE06 hybrid functional reveal an indirect bandgap of 0.98 eV and a type-II band alignment, which facilitate efficient spatial separation of photogenerated electron-hole pairs. The heterostructure shows excellent optical absorption in the visible region, with an absorption coefficient on the order of 105 cm-1. Further studies demonstrate that external electric fields and biaxial strain can effectively modulate its optoelectronic performance: tensile strain extends the absorption range into the infrared region, while an applied electric field raises the power conversion efficiency remarkably from 17.2% (under normal conditions) to 31.9%. Overall, these results indicate that the MoSi2P4/SnS2 heterostructure is a promising candidate for high-efficiency optoelectronic devices and offers new insights for the development of tunable photovoltaic cells.