Type-II MoSi2N4/MoS2 van der Waals Heterostructure with Excellent Optoelectronic Performance and Tunable Electronic Properties

van der Waals heterostructures (vdWHs) provide a new strategy to broaden the application of two-dimensional (2D) materials in novel nanodevices. Based on first-principles calculations, we propose a 2D MoSi2N4/MoS2 vdWH for light harvesting and photovoltaic applications. The MoSi2N4/MoS2 vdWH exhibits a semiconducting characteristic with an indirect band gap of 1.12 eV. The type-II band alignment of MoSi2N4/MoS2 vdWH facilitates the spatial separation of photogenerated electron–hole pairs. Therefore, the MoSi2N4/MoS2 vdWH exhibits excellent optical absorption (∼105 cm–1) and large photocurrent density (1.6 mA cm–2) in the visible range. Furthermore, performing external electric field and biaxial strain can effectively regulate the band gap and band alignment of MoSi2N4/MoS2 vdWH. Notably, the tensile strain significantly enhances the optical absorption and total photocurrent of MoSi2N4/MoS2 vdWH. These findings reveal the potential of MoSi2N4/MoS2 vdWH as a new alternative for optoelectronic devices and provide new possibilities for designing strain-tunable photovoltaic devices.