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 Wse₂ 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 (λ < 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 (~ 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. [ABSTRACT FROM AUTHOR]