Changes in electronic and optical characteristics of halogen-alkali adsorbed WSe2 monolayer

Adsorbing halogen and alkali metals atoms modify the optical and electrical characteristics of WSe2 monolayer (2D). The electrical and optical characteristics of the Wse(2) monolayer, alkali and halogen atoms adsorbed WSe2 structures are investigated through density functional theory (DFT) simulations. The pristine WSe2 monolayer has insignificant absorption in the infrared and most parts of the visible region, and substantial absorption in the ultraviolet (UV) region (lambda < 410 nm) as well as in a small section of the visible spectrum. The absorption coefficient of alkali-halogen adsorbed structures of WSe2 seems to expand with wavelength, and absorption peaks move toward the higher energy region of the optical spectrum, resulting in redshift effect. Significant absorption is observed in the entire visible spectrum ( similar to 410 to 780 nm) for both alkali and halogen adsorbed WSe2 nanostructures. The chlorine, bromine, and iodine adsorbed WSe2 structure shows larger absorption in the entire visible region among all other adsorbed structures. Presence of absorption peaks in the visible range of wavelengths rather than in the UV region, is beneficial for optoelectronic applications such as LEDs, CRTs, solar cells, and sensors. Trends in computed dielectric constant and refractive index values are also found to be compatible with trends in absorption coefficient values.

Automated summary

Using density functional theory (DFT) simulations, the electrical and optical characteristics of WSe2 monolayers with adsorbed alkali and halogen atoms were investigated. The results show that the absorption coefficient of the adsorbed structures increases with wavelength and the absorption peaks move towards the higher energy region of the optical spectrum. Chlorine, bromine, and iodine adsorbed WSe2 structures exhibit stronger absorption in the visible spectrum.