Electronic structures of anatase (TiO2)1-x(TaON)x solid solutions: a first-principles study.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Computational Chemistry

Background:

• Visible-light sensitization of wide band gap materials is crucial for solar energy conversion.
• Nitrogen doping in anatase TiO2 is limited by aliovalent substitution, causing defects and hindering charge carrier migration.
• Developing stable, efficient visible-light absorbers remains a significant challenge.

Purpose of the Study:

• To investigate the electronic structures of (TiO2)1-x(TaON)x solid solutions within the anatase crystal structure.
• To assess the potential of these solid solutions as visible-light absorbers for enhanced solar energy conversion.
• To understand how co-substitution of Ti for Ta and O for N affects the band gap and electronic properties.

Main Methods:

• First-principles calculations were employed to study the electronic structures of (TiO2)1-x(TaON)x solid solutions.
• The anatase crystal structure was used as the basis for the computational investigation.
• Analysis of band gap, valence band maximum (VBM), and conduction band minimum (CBM) was performed.

Main Results:

• The (TiO2)1-x(TaON)x solid solutions exhibit substantially narrower band gaps compared to pristine TiO2.
• A direct band gap is achieved when the TaON content exceeds 0.25, enhancing light absorption.
• The valence band maximum shifts to higher energy due to N 2p hybridization, while the conduction band minimum is lowered by d-d bonding states.

Conclusions:

• The anatase (TiO2)1-x(TaON)x solid solutions are promising visible-light absorbers.
• Co-substitution of Ti for Ta and O for N effectively narrows the band gap without introducing detrimental localized states.
• These materials offer a viable strategy for improving solar energy conversion efficiency through visible-light absorption.