ψ-Phosphorene: a new allotrope of phosphorene

Based on the crystal structure prediction, we propose a new allotrope of phosphorene, ψ-phosphorene (ψ-P), with a porous structure, which is both thermally and dynamically stable in comparison with the previously reported allotropes. Due to its unique atom configuration, ψ-P has highly orientation-dependent mechanical properties and excellent flexibility. Calculations using the HSE functional predict that ψ-P is semiconducting with an indirect band gap of 1.57 eV and possesses anisotropic transport properties. Particularly, the electron mobility along the x-direction is up to 1.3 × 10⁴ cm² V^-1 s^-1, which is comparable with that of black phosphorene. Considering its intrinsic porous structure, the performance of monolayer ψ-P as a gas purification membrane was investigated. The calculation demonstrates that ψ-P could be used for hydrogen purification from the mixture of CH₄, CO₂, N₂, CO, and H₂ with high selectivity. Furthermore, combining a suitable band gap with high carrier mobility, a MoSe₂/ψ-P van der Waals heterojunction is predicted to be a good solar cell material, whose power conversion efficiency is estimated up to 20.26%. Finally, we demonstrated that the Au(110) surface could be a suitable substrate for the synthesis of ψ-P.