van der Waals (vdW) heterojunctions are of interest in two-dimensional electronic and optoelectronic devices.

Van der Waals (vdW) heterojunctions constructed using two-dimensional (2D) materials have shown excellent properties for applications in various fields. In this study, the structural and electronic properties of 2D MoSe2/C3N and WSe2/C3N vdW heterojunctions were investigated using first-principles calculations. The results show that the MoSe2/C3N heterojunction is an indirect bandgap semiconductor with a small bandgap 0.05 eV and the WSe2/C3N heterojunction is a type II heterojunction with an indirect bandgap of 0.26 eV. Strains and external electric fields can effectively modulate the electronic structure of these heterojunctions. The WSe2/C3N heterojunction can become a type III heterojunction under compressive strain, which becomes a direct bandgap heterojunction with type I band alignment under a negative electric field. Our results may be useful for the design of electronic nanodevices.