A first-principles investigation of the electronic, dielectric, and optical properties of two-dimensional (2D) monolayer transition metal dichlorides

Many novel materials with unique properties have been recognized in the two-dimensional (2D) materials family. The scientific community is investigating the suitability of these materials for possible applications. Using the density functional theory, the present work investigated the electronic, dielectric, and optical properties of four binary transition metal dichlorides (CdCl₂, FeCl₂, PdCl₂, and ZnCl₂) for their possible device applications. The electronic properties show that these are wide-bandgap materials. The optical and dielectric properties were studied in the incident photon energy range of 0–40 eV for the in-plane (parallel) and out-of-plane (perpendicular) light polarization directions. The optical analyses reveal that these are excellent absorbers of the incident light in the ultraviolet region of electromagnetic (EM) radiation, consistent with a high extinction coefficient for the corresponding incident photon energy. Moreover, these materials exhibit optical and dielectric anisotropy. It is observed that the PdCl₂ is a biaxial optical birefringent material, whereas others are uniaxial. These are also good candidates for constructing reflection, transmission, and absorption edge/band filters in the different regions of the EM spectrum. Among these, the ZnCl₂ exhibits excellent antireflective properties. Therefore, the present study shows the potential applications of these materials in electronic and optoelectronic devices. This study also provides a way to characterize them for further experimental analysis.