Janus MoAZH (A = Ge, Si; Z = N, P, As) monolayers: a new class of semiconductors exhibiting excellent photovoltaic and catalytic performances.

Due to the asymmetrical structure in the vertical direction, Janus two-dimensional (2D) monolayer (ML) materials possess some unique physical properties, holding great promise for nanoscale devices. In this paper, based on the newly discovered MoAZ (A = Si, Ge; Z = N, P, As) ML, we propose a class of 2D Janus MoAZH ML materials with good stability and excellent mechanical properties using first-principles calculations. We demonstrate that the novel Janus MoAZH ML materials are all semiconductors with bandgaps ranging from 0.69 to 2.44 eV, giving rise to good absorption in the visible light region. Especially, both MoSiNH and MoGeNH MLs can be used as catalysts for producing hydrogen through water splitting. This catalytic property is much more efficient than that of the MoAZ ML, attributed to the intrinsic electric field induced by the vertical asymmetry effectively separating electrons and holes. More importantly, the carrier mobility of the MoAZH ML is up to 10-10 cm V s due to the large elastic modulus or small effective mass. Additionally, the electronic properties of the MoAZH ML can be easily tuned by strain. Our results suggest a new strategy for designing novel 2D Janus materials, which not only expands the members in the 2D MAZ-based Janus family, but also provide candidates with excellent performances in photovoltaic and catalytic fields.