Electronic structure and optical property of Cd $$_{2-x}$$ 2 - x Y $$_{x}$$ x SnO4 using the first-principles calculation

The electronic structure and optical properties of Cd2-xYxSnO4 are studied using the first-principle calculation within the generalized-gradient approximation and the Coulomb repulsion effect. Three defect models are constructed by Y atom occupying Cd sites. The energy band shows that the 4d electrons of Y atom mainly affect the bottom of conduction band. The density of state reveals that the 4d state of Y atom hybridizes with the O 2p and Cd 5s states at the bottom of conduction band. With the increment of the substitution numbers, Y 4d states increases gradually to enhance the hybrid intensity. The average effective mass of Cd1.875Y0.125SnO4 model attains 0.352m0, which is lower than 0.484m0 of Cd2SnO4. It indicates that the conductivity of Cd2SnO4 is improved by Y occupying Cd site. Moreover, the absorption edges of Cd1.9375Y0.0625SnO4 and Cd1.875Y0.125SnO4 models blueshift to induce optical transmittance reaching about 90% in the visible light region. Therefore, Cd1.875Y0.125SnO4 can be applied to prepare a short wavelength optical device in future. Graphical abstract As the substitution concentration increases, both the conduction band and the valence band move to the low energy direction. The band gap value of Cd1.9375Y0.0625SnO4 is 2.19 eV, which is the closest to the band gap value of Cd2SnO4. The band gap value decreases slightly with increasing substitution concentration of Y at Cd site. Compared with the effective mass m* of Cd2SnO4, the effective mass m* decreases after the entry of Y atoms. It indicates that Y atoms substitution has a certain improvement for the conductivity of Cd2SnO4. The transmittance of Cd1.9375Y0.0625SnO4 and Cd1.875Y0.125SnO4 models can attain 90%, which is somewhat higher than that of Cd2SnO4.