First Principles Calculations of Structural, Electronic and Optical Properties of Nitrogen-Doped Titanium Dioxide for Solar Cells Application

Abstract

Buhari Aminu Balesa, Abdullahi Lawal, Saddiq Abubakar Dalhatu ,Bala Idris and Mustapha Bello

The dire requirement for less toxic, eco-friendly, cheaper, cost-effective, and efficient material for solar cell application has led to increasing focus on a range of different source materials. In particular, the larger energy bandgap in TiO₂ has limited its application for solar cell applications. However, doping TiO₂ with non-metal such as N gives a broader absorption at the visible region and subsequently adjusts the bandgap, which allows better utilization of the solar spectrum. However, to exploit its potentials, a detailed analysis of structural, electronic, and optical properties of N doped TiO₂ is necessary. In this work, first-principles calculations within the density functional theory (DFT) are carried out as an approach to address the problem. The calculated band gap energy for pure TiO₂ (2.30 eV) was in strong agreement with the experimental value.  The substitution of nitrogen (N) atom in the TiO₂ at the oxygen (O) and titanium (Ti) sites led to the reduction in the energy gap and the observation was also in good agreement with results from previous works. Our findings confirmed that non-metal doping narrows the energy band gap of semiconductor materials. The optical gap of 1.63 and 0.32 eV for N doped TiO₂ at oxygen (O) and titanium (Ti) sites, which indicated that N-dopedTiO₂ can be used to detect light in the near infrared and visible light regions. Direct energy gap, narrowing effects, and strong light absorption of N-doped TiO₂ in the near infrared to visible light region suggest that the investigated material is most likely suitable for solar cells and near-infrared optoelectronic applications