First-Principles Studies of Strain-Adjustable Janus WSSe Monolayer/g-GeC Monolayer Heterojunctions: Implications for Photoelectric and Switching Devices

Two-dimensional heterojunction materials show great potential for a wide range of applications with their tunable properties, such as versatility and low-dimensional confinement effects. The electronic structure, transport, and optical properties of Janus WSSe/g-GeC heterojunctions are investigated in-depth using density functional theory combined with a nonequilibrium Green's function approach. The results show that the electronic properties of Janus WSSe/g-GeC heterojunction materials can be effectively tuned by applying vertical and biaxial strain. In particular, when a biaxial strain of ±10% is applied, it can transform the heterojunction from semiconductor properties to metallic properties. In addition, we found that a Janus WSSe/g-GeC heterojunction exhibits excellent optical properties with a strong absorption peak in the visible region. In this heterojunction-based PIN junction, considerable photocurrents are generated in the visible range, especially in the region of 1.7 to 3.1 eV, where significant photocurrent density peaks appear, and the vertical strain can effectively modulate the photocurrent density peaks. In addition, a Janus WSSe/g-GeC heterojunction-based device exhibits excellent performance with a high current switching ratio of 1011 at the biaxial strain of ±10%, showing perfect diode behavior. In summary, by tuning the applied strain, its electronic properties can be effectively tuned and exhibit excellent optical response. Janus WSSe/g-GeC heterojunction materials have great potential for optoelectronic and switching devices. These findings provide important references and guidance for further development of practical applications based on WSSe/g-GeC heterojunctions.