Interface and strain engineering of band alignment and photovoltaic performance in NbSiN 3 /NbGeN 3 van der Waals heterostructures

Abstract Interfacial charge redistribution and strain modulation are crucial for tailoring the electronic structure and optoelectronic properties of two-dimensional van der Waals heterostructures. In this work, first-principles calculations are employed to investigate the interface- and strain-dependent electronic and optical properties of NbSiN 3 /NbGeN 3 heterostructure. The structural stability of various stacking configurations is confirmed through cohesive energy and phonon dispersion analyses, while electrostatic potential profiles reveal the interfacial polarization direction. The Ge/Nb, Ge/Si, and Nb/Si stacking configurations exhibit type-II band alignment, which promotes efficient spatial separation of photoexcited carriers. Especially, the Ge/Si configuration shows exceptionally high hole mobility, reaching 11318 cm 2 ·V −1 ·s −1 along the x direction and 7297 cm 2 ·V −1 ·s −1 along the y direction. Furthermore, biaxial tensile strain effectively tunes the band edges and enhances the photovoltaic response, achieving a maximum theoretical power conversion efficiency of approximately 21.9%. These findings provide physical insight into interface and strain engineered band alignment and offer guidance for designing high-performance optoelectronic nanodevices.