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

Abstract

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 ΔGH 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.

Keywords

• Thermoelectric
• Water splitting
• Janus Ga2SSe
• Van der Waals heterostructures
• First-principles calculations