  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.

Mesoscale and Nanoscale Physics;Materials Science