A DFT Study on Electronic and Optical Properties of La/Ce-Doped CaTiO₃ Perovskite

CaTiO₃ perovskite has drawn extensive attention in recent years for its photocatalytic applications related to environmentally friendly fields, such as photodegradation of organic pollutants, carbon dioxide reduction, etc. However, most research was focused on the experimental modification strategies for increasing its photo-catalytic efficiency, little is known about the mechanisms behind it, especially at the molecular level. Our focus here, is the electronic and optical properties of La/Ce-doped CaTiO₃ perovskite with different mass fractions. A 2 × 2 × 2 supercell of La/Ce-doped CaTiO₃ with concentrations of 2.5 wt% and 5 wt% were modeled and optimized by GGA-PBE functional with a cutoff energy of 571.4 eV in CASTEP. The lattice parameters, electronic structures and optical properties were then calculated. Our results show that the Ce-doped CaTiO₃ formed more stable structures than La-doped ones, with the minimum formation energy achieved at a doping concentration of 5 wt%; Additionally, for both La and Ce-doped cases, a higher doping concentration (5 wt%) results in a better potential structure for an n-type material, with its conduction band shifting across the Fermi level. The shift was caused by the adjustment of the band structure with the introduction of rare earth elements, which indirectly influenced the Ti-d-states of CaTiO₃. According to our optical property studies, La/Ce doping in CaTiO₃ could also reduce polarization and refractive index compared to pure CaTiO₃. Our work provides a theoretical framework to study how different types and concentrations of doping elements affect the photophysical properties of CaTiO₃ perovskite.