Oxygen vacancy and doping atom effect on electronic structure and optical properties of Cd2SnO4
The electronic structure and optical properties of oxygen vacancy and La-doped Cd2SnO4 were calculated using the plane-wave-based pseudopotential method based on the density functional theory (DFT) within the generalized gradient approximation (GGA). The formation energy of different oxygen vacancies showed that the VO2 oxygen vacancy was easy to obtain in experiments. The Bader charge analysis is implemented to directly observe the electron transfer and distribution for each atom. The calculated band structures show that when the oxygen vacancy was introduced, the impurity energy level appeared in the band gap. The impurity levels induced by oxygen vacancies were mainly composed of O 2p orbits and a very small amount of Cd 4s orbits. After La doping based on the VO2 oxygen vacancy of Cd2SnO4, the Fermi energy level entered the conduction band and overlapped with the conduction band which increased the conductivity, and the band gap value increased to above 3.0 eV. The optical calculation results showed that the transmittance of the VO2 oxygen vacancy of Cd2SnO4 increased in short wavelength (<600 nm), the reflectivity increased in the infrared region compared with Cd2SnO4, and the transmittance increased to 90% in visible light region after La doping.