Theoretical investigations of electronic structure and optical properties of S, Se or Te doped perovskite ATiO3 (A=Ca, Ba, and Sr) materials for eco-friendly solar cells

Structural, electronic, and optical properties of undoped and chalcogens doped ATiO3 (A ​= ​Ca, Ba, and Sr) materials are studied using Density Functional Theory and Local Density Approximation with modified Becke and Johnson to explore the effect of S, Se or Te doped ATiO3 perovskites. Our results show that after the substitution of S, Se, or Te elements in oxygen sites, the bandgap widths are decreased with increasing the doped concentrations up to 7.5%, conserving the p-type semiconductor behavior because the number of the core orbital in the pure structures are the same in the doped structures (after the substation of oxygen atoms O (2s22p6) by chalcogens' orbitals S (3s3p6), Se (4s24p6) and Te (5s25p6)). Therefore, the absorption coefficient and the optical conductivity of the doped systems are boosted in the photovoltaic range, especially for BaTiO3 doped with 2.5% and 5% of Te making BaTiO3Te more favorable for the photovoltaic devices compared to CaTiO3Te and SrTiO3Te compounds.