Investigation of 2D Janus Al₂OS/Ga₂SSe van der Waals heterojunction as next-generation thermoelectric and photocatalytic devices

Using first−principles DFT calculations and taking into account the impact of in−plane biaxial strain, we thoroughly explore the optical, electronic, mechanical, transport, and photocatalytic properties of Al₂OS/Ga₂SSe vdWH. The most stable configuration of Al₂OS/Ga₂SSe vdWH is mechanically, thermally and dynamically stable. Moreover, Al₂OS/Ga₂SSe vdWH gives rise to an indirect semiconductor band gap (2.34 eV). The vdWH forms type−II band alignment, indicating that the photogenerated carriers are spatially separated due to the internal electric field, thus enhancing the photocatalytic performance. The results show that Al₂OS/Ga₂SSe vdWH under biaxial strain of ± 4% at pH = 0 is a promising candidate for water splitting. More importantly, it was found that the ΔG_H of Al₂OS/Ga₂SSe vdWH (−0.18 eV) is smaller than those of the monolayers. Moreover, Al₂OS/Ga₂SSe vdWH has remarkably higher electrical conductivity than corresponding monolayers in n − type doping region, responsible for large power factor and suitable Seebeck coefficient, making it promising for thermoelectric device applications. It is worth noting that the vdWH offers important theoretical guidance for the development of next−generation optoelectronics, thermoelectric and solar energy devices.