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

TL;DR

This study uses first-principles density functional theory to explore how platinum incorporation affects the electronic properties of anatase TiO2(001) surfaces, aiming to enhance visible light absorption for solar cell applications.

Contribution

It provides a systematic analysis of Pt impurity configurations on anatase TiO2(001) surfaces and their impact on electronic structure and band gap reduction.

Findings

Pt interstitials form metallic wires inside the surface.

Substitutional Pt narrows the band gap by ~1.5 eV.

Pt incorporation can make TiO2 responsive to visible light.

Abstract

First-principles density functional theory calculations were carried out to determine the low energy geometries of anatase TiO$_2$(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 1x1 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 2x2 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 2x2 surface models exhibit flat-like defect states driven from the valence bands narrowing the energy gap suitable to obtain visible light responsive titania.