Pt-incorporated anatase TiO2 (001) surface for solar cell applications: First-principles density functional theory calculations

Abstract

First-principles density functional theory calculations were carried out to determine the low energy geometries of anatase TiO2(001) with Pt implants in the sublayers as substitutional and interstitial impurities as well as on the surface in the form of adsorbates. We investigated the effect of such a systematic Pt incorporation in the electronic structure of this surface for isolated and interacting impurities with an emphasis on the reduction in the band gap to visible region. Comprehensive calculations, for 1×1 surface, showed that Pt ions at interstitial cavities result in local segregation, forming metallic wires inside, while substitution for bulk Ti and adsorption drives four strongly dispersed impurity states from valence bands up in the gap with a narrowing of ∼1.5 eV. Hence, such a contiguous Pt incorporation drives anatase into infrared regime. Pt substitution for the surface Ti, on the other hand, metallizes the surface. Systematic trends for 2×2 surface revealed that Pt can be encapsulated inside to form stable structures as a result of strong Pt-O interactions as well as the adsorptional and substitutional cases. Dilute impurities considered for 2×2 surface models exhibit flatlike defect states driven from the valence bands narrowing the energy gap suitable to obtain visible-light responsive titania.