Tailoring the structural, elastic, electronic, and optical properties of TiO2via carbon doping: a first-principles study

Abstract

A detailed computational study employing density functional theory (DFT) was undertaken to investigate the structural, electronic, elastic, and optical properties of carbon-doped titanium dioxide (TiO₂). We optimized atomic structures using the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation (GGA). The calculated size of the crystal lattices (lattice parameters) for pure and carbon-doped TiO₂ were in excellent agreement with previously reported theoretical and experimental values, validating our computational approach. Formation-energy calculations confirmed the thermodynamic stability of undoped and carbon-doped TiO₂, as demonstrated by the negative formation energies we observed at a 3.15% doping concentration. Replacing oxygen atoms with carbon atoms led to a noticeable reduction in the band gap (the energy electrons need to jump to conduct), ∼0.3 eV for lower doping levels. This reduction occurred because the carbon atoms introduced new energy levels (impurity states) near the highest energy level of the valence band. This, in turn, significantly increased the ability of the material to absorb visible light. Our simulations also revealed that carbon doping changed the electronic structure remarkably, leading to improved mobility of charge carriers and extending the light absorption of the material into the visible range. These findings strongly suggest that carbon-doped TiO₂ is a promising material for next-generation optoelectronic and photocatalytic devices.