TDDFT studies on effects of the size on optoelectronic properties of 2D germanene sheets

We report on the TDDFT calculations of the effect of the size on the optoelectronic properties of germanene sheets. Five structures of germanene were considered. All structures were optimized and their electronic and optical properties are studied using B3LYP functional with 6–31G basis set. Frequency and energy calculations were carried out to yield the Density of States (DOS), IR and UV-VIS spectra. It was seen that the structures had size tunable spectral response in the ultraviolet spectrum. The wavelengths vary from 225 nm to 310 nm as the sheet size increases.