Tuning electronic and optical properties of monolayer PdSe₂ by introducing defects: first-principles calculations

Based on the density functional theory, the electronic and optical properties of pristine monolayer PdSe₂ with Pd or Se vacancy-defect are investigated. Our results show that the Se defect is energetically more favorable than that of Pd defect. The band gap reduces, and some new midgap states appear after the Pd or Se defects are introduced. In terms of the optical properties, the prominent anisotropic characters are remained. The obvious new peaks of the dielectric constant appear after introducing defects. The light absorption in the visible energy range expands based on the appearance of the midgap states induced by the Pd or Se defects. The changes of the refractive index and reflectivity are similar with those of the dielectric constants and the light absorption. The energy loss spectrum of the PdSe₂ with Pd or Se defects is obviously different, which can be used to identify different defects in PdSe₂. These findings provide effective strategies to tune electronic and optical properties of monolayer PdSe₂ by introducing defects.