Structural, Electronic, and Optical Properties of Group 6 Doped Anatase TiO2: A Theoretical Approach

Abstract

Titania (TiO2) is a key material used as an electron transport in dye-sensitized and halide perovskite solar cells due to its intrinsic n-type conductivity, visible transparency, low-toxicity, and abundance. Moreover, it exhibits pronounced photocatalytic properties in the ultra-violet part of the solar spectrum. However, its wide bandgap (around 3.2 eV) reduces its photocatalytic activity in the visible wavelengths’ region and electron transport ability. One of the most efficient strategies to simultaneously decrease its bandgap value and increase its n-type conductivity is doping with appropriate elements. Here, we have investigated using the density functional theory (DFT), as well as the influence of chromium (Cr), molybdenum (Mo), and tungsten (W) doping on the structural, electronic, and optical properties of TiO2. We find that doping with group 6 elements positively impacts the above-mentioned properties and should be considered an appropriate method for photocatalystic applications. In addition to the pronounced reduction in the bandgap values, we also predict the formation of energy states inside the forbidden gap, in all the cases. These states are highly desirable for photocatalytic applications as they induce low energy transitions, thus increasing the oxide’s absorption within the visible. Still, they can be detrimental to solar cells’ performance, as they constitute trap sites for photogenerated charge carriers.

Structural, electronic and optical DFT investigation of ruthenium doped anatase TiO2 for photocatalytic applications

“…67 which is in good agreement with the experimental value of 4.5[47] and other calculation works[48,49]. For RuTi 15 O 32 system, ( ) 0 1 e w = decreases in both x and z direction to about 2.89.…”

High anisotropic magnetoresistance, perfect spin-filtering effect, and negative differential resistance effect of Cr-doped anatase phase TiO2

“…We use SGGA + U and choose 10 × 10 × 5 k-point meshes in the geometry optimizations. We set U = 3 eV cause previous studies have shown that is sufficient for transition metal-doped anatase [44][45][46]. The force is less than 0.02 e V/Å −1 on each atom, and the calculation will be terminated till the energy is less than 10 -5 eV.…”

“…Experimental results show that atom replacement doping is an effective way to generate magnetic properties and adjust the band gap [14,15]. Doping is applied to reduce the band gap of anatase as a strategy that can modulate the band gap effectively [16,17]. In the work of Aguilera del Toro et al [18], they succeeded in reducing the band gap by replacing the metal or non-metal in (TiO 2 ) 10 to control the impurity content.…”