Self energy and excitonic effect in (un)doped TiO₂ anatase: a comparative study of hybrid DFT, GW and BSE to explore optical properties

Abstract

TiO2 anatase has its significant importance in energy and environmental research. However, the major drawback of this immensely popular semi-conductor is its large bandgap of 3.2 eV. Several non-metals have been doped experimentally for extending the TiO2 photo-absorption to the visible region. Providing in-depth theoretical guidance to the experimentalists to understand the optical properties of the doped system is therefore extremely important. We report here using state-of-theart hybrid density functional approach and many body perturbation theory (within the frame work of GW and BSE) the optical properties of p-type (S and Se doped) and n-type (N and C doped) TiO2 anatase. The anisotropy present in non-metal doped TiO2 plays a significant role in the optical spectra. The p-type dopants are optically active only for light polarized along xy direction, whereas the n-type dopants are optically active when light is polarized along xy and z direction in low energy region. We have found that, in all the doped systems optically allowed transitions are introduced well below 3 eV (i.e. visible spectra region). This helps to improve its opto-electronic and solar absorption properties. All the calculations are well validated with respect to the available experimental observation on pristine TiO2 anatase.

MoS2and Janus (MoSSe) based 2D van der Waals heterostructures: emerging direct Z-scheme photocatalysts

“…5 gives the absorption spectra obtained from imaginary part of the dielectric function as computed by GW method (G 0 W 0 @HSE06). The dielectric function is a frequency dependent complex function (ε(ω) = Re(ε) + Im(ε)) where the real part (Re(ε)) is computed from the Kramers-Kronig relation and the imaginary part (Im(ε)) is obtained from the interband matrix elements in the momentum space 81 . Since, the interband process consists of transitions to the unoccupied orbitals, the Im(ε) gives the absorption spectra.…”

Theoretical insights of codoping to modulate electronic structure of $$\hbox {TiO}_2$$ and $$\hbox {SrTiO}_3$$ for enhanced photocatalytic efficiency

“…Therefore, the optical anisotropy is also associated with it. The detailed discussion of optical anisotropy is already done in our previous work 74 . Therefore, here we have shown only the averaged (x, y, z polarizations) for imaginary and real part of the dielectric function.…”

Exploring Exciton and Polaron Dominated Photo-physical Phenomena in Ruddlesden-Popper Phases of Ban+1ZrnS3n+1 (n=[1-3]) from Many Body Perturbation Theory

“…We have executed a systematic study to explore the optical, electronic and excitonic properties using Density Functional Theory (DFT) 32,35 and beyond approaches under the framework of Many Body Perturbation Theory [53][54][55] . All calculations are performed with Projected Augmented Wave (PAW) potentials as implemented in Vienna Ab initio Simulation Package (VASP) 56,57 .…”