Electronic and optical properties of new Pentagonal Janus PtXY (X, Y=S, Se, Te; X ≠ Y) monolayers: A DFT study

In this work, we investigate a new phase of two-dimensional Janus PtXY (X, Y= S, Se, Te; X≠ Y) monolayers named pentagonal (Penta-PtXY) using the first-principles calculations. We found that Penta-PtXY monolayers are semiconductors with an indirect band gap of 1.69 eV, 1.52 eV, and 1.43eV for Penta-PtSSe, Penta-PtSTe, and Penta-PtSeTe, respectively, that is reduced with the inclusion of spin–orbit coupling. These structures are dynamically stable as their phonon dispersions showed no soft phonon frequencies. The investigation of the optical properties revealed that monolayers Penta-PtXY have in-plane anisotropic optical properties with higher absorption spectra along the y-direction. Moreover, the maximum absorption occurs in the ultraviolet (UV) region, therefore, they can harvest UV and visible photons more effectively. This combination of properties makes these materials attractive for fundamental studies of anisotropic phenomena in 2D materials and may enable novel optoelectronic and nanotechnology applications.