Strain and spin orbit coupling effects on electronic and optical properties of 2D CX/graphene (X = S, Se, Te) vdW heterostructure for solar energy harvesting

Vertically stacked two-dimensional (2D) graphene-based van der Waals (vdW) heterostructures have emerged as the technological materials for electronic and optoelectronic device applications. In this regard, for the first time, we systematically predicted the electronic and optical properties of CX/G (X = S, Se and Te; G = graphene) heterostructures under biaxial strain and spin orbit coupling (SOC) by first-principles calculations. Strain is induced by applying mechanical stress to the heterostructures, while SOC arises due to the interaction between the electron spin and its orbital motion. The electronic property calculations reveal that all three heterostructures exhibit indirect semiconducting nature with a narrow bandgap of 0.47-0.62 eV and remain indirect under compressive and tensile strains. Strong band splitting of 78.4 meV has been observed in the conduction band edge of CTe/G heterostructure in the presence of SOC due to the lack of an inversion center attributed to the large hole effective mass. Under compressive strain, the p-type of Schottky contact of CX/G heterostructures is converted into p-type Ohmic contact because of nearly negligible Schottky barrier height. Further, the optical property assessment reveals red and blue shifts in the absorption peak of CX/G heterostructures with regard to tensile and compressive strains, respectively. Despite this, the CTe/G heterostructure achieves a remarkable high {\eta} of 24.53% in the strain-free case whereas, it reaches to 28.31% with 4% compressive strain, demonstrating the potential for solar energy conversion device applications. Our findings suggest that CX/G heterostructures could be promising candidates for high-performance optoelectronic devices.