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 MoSi 2 N 4 /MoS 2 vdWH for light harvesting and photovoltaic applications. The MoSi 2 N 4 /MoS 2 vdWH exhibits a semiconducting characteristic with an indirect band gap of 1.12 eV. The type-II band alignment of MoSi 2 N 4 /MoS 2 vdWH facilitates the spatial separation of photogenerated electron–hole pairs. Therefore, the MoSi 2 N 4 /MoS 2 vdWH exhibits excellent optical absorption (∼10 5 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 MoSi 2 N 4 /MoS 2 vdWH. Notably, the tensile strain significantly enhances the optical absorption and total photocurrent of MoSi 2 N 4 /MoS 2 vdWH. These findings reveal the potential of MoSi 2 N 4 /MoS 2 vdWH as a new alternative for optoelectronic devices and provide new possibilities for designing strain-tunable photovoltaic devices.