Tunable electronic and optical properties of GeC/g-C₃N₄ vdWH by electric field and biaxial strain

van der Waals heterostructures (vdWHs) show great potential for optoelectronic devices and photocatalysis. This work investigates the stability, electronic structure and optical properties of GeC/g-C₃N₄ using first-principles and considers the role of external electric fields and biaxial strain in the heterostructure. The results show a reduced band gap of GeC/g-C₃N₄ vdWH with strong optical absorption in the visible light range compared to monolayer GeC and g-C₃N₄. The heterostructure is a type-II semiconductor that is extremely suitable for the development of optoelectronic devices and photocatalytic materials. The external electric field can flexibly tune the band gap and band alignment of GeC/g-C₃N₄ vdWH, enabling it to transition between type-I, type-II and type-III. Biaxial strain effectively tunes the band structure of GeC/g-C₃N₄ vdWH, reducing the band gap and further increasing optical absorption capacity. These results suggest that external electric fields and biaxial strain are effective ways to tune GeC/g-C₃N₄ vdWH, providing a theoretical basis for relevant experimental preparation.