SeWS/bilayer-SiC heterojunction: an S-scheme photocatalyst with high visible-light absorption, excellent carrier mobility, and adjustable band gap

Abstract Vertically stacked heterojunctions have garnered significant attention for their tunable electronic structures and photocatalytic performance, making them promising candidates for next-generation nanodevices. Using first-principles calculations, we systematically investigate the electronic structure, optical characteristics, and charge transfer of WSSe/SiC heterojunctions. Our results reveal that SeWS/monolayer-SiC, SeWS/bilayer-SiC, and SWSe/monolayer-SiC exhibit type-II band alignment, whereas SWSe/bilayer-SiC displays type-I alignment. Notably, SeWS/bilayer-SiC possesses a direct bandgap, in contrast to the indirect band gaps of the other three configurations. Remarkably, the SeWS/bilayer-SiC heterojunction demonstrates a high absorption coefficient (10 5 cm −1 ) in the visible range and exhibits exceptional anisotropy in carrier transport, with an outstanding hole mobility of 9.58 × 10 3 cm 2 V −1 s −1 along the Y direction. Furthermore, by combining thermodynamic stability with the S-type charge transfer mechanism, this system demonstrates outstanding redox capabilities in photocatalytic water splitting, showing a hydrogen production efficiency potential of up to 22.15%, exceeding the commercial feasibility threshold (10%). Additionally, we have also demonstrated that external electric fields and biaxial strain can effectively regulate the band gap, and the optical absorption coefficient exhibits a strong dependence on strain. This work offers fundamental insights for designing WSSe/SiC heterojunctions that enable efficient photocatalysis and tunable photodetector applications.