Tailoring the anisotropic effect of Janus In2 XY (X/Y = S, Se, Te) monolayers toward realizing multifunctional optoelectronic device applications

Anisotropic effect of two-dimensional materials remains one of the most attractive properties, introducing an additional degree of freedom for tuning physical performances. In this work, we investigate the anisotropies of electronic, transport, piezoelectric, and optoelectronic properties of Janus In _2 XY ( X / Y = S, Se, Te) monolayers (J-In _2 XY MLs) by performing first-principles calculations. We find that such J-In _2 XY MLs possess moderate bandgap (2.07–2.29 eV), high carrier mobility (∼10 ^3 cm ^−2 V ^−1 s ^−1 ), visible light absorption (∼10 ^5 cm ^−1 ), large out-of-plane piezoelectric response $({d_{31}} = 0.35{\text{ pm}}\;{{\text{V}}^{ - 1}}{\text{)}}$ and ultra-soft mechanical nature $({C_{11}} = 32.84{\text{ N}}\;{{\text{m}}^{ - 1}}{\text{)}}$ . We construct a kind of J-In _2 XY- based phototransistor to investigate the optoelectronic properties under linearly polarized light. We find that the low recombination probability of photogenerated carriers ensured by anisotropic effect enhances the photocatalytic potential of J-In _2 XY MLs. And the pivotal role induced by anisotropy in photocurrent can cause a prominent on/off ratio (∼100), considerable responsivity (0.038 AW ^−1 , 0.036 AW ^−1 ) and external quantum efficiency (10.6%, 11.5%). Our study provides an avenue for the design of future anisotropic J-In _2 XY- based multifunctional optoelectronic device.