Electric field and strain effects on the electronic and optical properties of g-C3N4/WSe2 van der Waals heterostructure

Abstract

Efficient carrier separation and regulable visible light absorption are important characteristics for eligible nanoscale photoelectric devices. In this work, tunable electronic structure and optical properties of novel g-C3N4/WSe2 van der Waals heterostructure under various electric fields and biaxial strains are systematically investigated by first principle calculations. The results show that the g-C3N4/WSe2 heterostructure is a direct band gap semiconductor (1.395 eV) with intrinsic type-I band alignment and exhibits good UV and visible light absorption compared to the isolated g-C3N4 and WSe2 monolayers. Applied external electric-field can effectively adjust the interlayer coupling and charge transfer, which can further alter the band structure and achieve the transition of type I to type II band alignment for the g-C3N4/WSe2 heterostructure. The biaxial strain causes charge redistribution in the interfacial regions and triggers an indirect-direct band gap transition in the g-C3N4/WSe2 heterostructure, which is strongly associated with the modification of band structure contributed by W dz2 and dxy orbitals near the Fermi level. Besides, the systematical red shift and blue shift of absorption peaks is also observed under the tensile and compressive strains, respectively. The tunable electronic structure and optical properties make g-C3N4/WSe2 vdW heterostructure potential candidates for application in the photoelectronic device.