In this paper, the electronic structure and optical properties of silicene sheet in the presence of different perpendicular electric fields are studied using density functional theory. A direct band gap at the K point can be created in silicene by applying a perpendicular electric field. Also, the linear dispersion characteristic of bands near the Fermi level remains unchanged under electric field. The size of opened band gap increases with the electric field strength. For silicene sheet without electric field, three major peak can be observed in the 2 ( ) spectrum at 0.2, 1.6 and 3.9 eV. The perpendicular electric field only affects the optical spectra in the low energy range below 1 eV. In the low energy range below 1 eV, the peak is blue shifted and its intensity decreases under application of electric field. Thus, the biased silicene is particularly interesting material for device applications such as tunneling field effect transistor.
