A comparative study on the electronic and optical properties of Sb$_{2}$Se$_{3}$ thin film

The thin film of Sb$_{2}$Se$_{3}$ was deposited by thermal evaporation method and the film was annealed in N$_{2}$ flow in a three zone furnace at a temperature of 290$^\circ$C for 30 min. The structural properties were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy, respectively. It is seen that the as-deposited film is amorphous and the annealed film is polycrystalline in nature. The surface of Sb$_{2}$Se$_{3}$ film is oxidized with a thickness of 1.15 nm investigated by X-ray photolecetron spectroscopy (XPS) measurement. Spectroscopic ellipsometry (SE) and UV-vis spectroscopy measurements were carried out to study the optical properties of Sb$_{2}$Se$_{3}$ film. In addition, the first principles calculations were applied to study the electronic and optical properties of Sb$_{2}$Se$_{3}$. From the theoretical calculation it is seen that Sb$_{2}$Se$_{3}$ is intrinsically an indirect band gap semiconductor. Importantly, the experimental band gap is in good agreement with the theoretical band gap. Furthermore, the experimental values of n,k,varepsilon$_{1}$, and varepsilon$_{2}$ are much closer to the theoretical results. However, the obtained large dielectric constants and refractive index values suggest that exciton binding energy in Sb$_{2}$Se$_{3}$ should be relatively small and an antireflective coating is recommended to enhance the light absorption of Sb$_{2}$Se$_{3}$ for thin film solar cells application.