Probing the role of bound excitons in optical properties of titanium dioxide anatase from first principles

The electronic structure and optical spectra of anatase titanium dioxide is computed by combining state-of-the-art density functional theory (DFT) and many-body perturbation theory (MBPT). Excitonic optical spectra is computed by solving Bethe-SalpeterEquation (BSE). From the solution of BSE and also from the analysis of charge distribution the photo-generated excitons in anatase is shown to be strongly bound and localized. Such typical behavior of intrinsic excitons in bulk anatase makes it a material which shows superior performance in photo catalysis, photovoltaics, optoelectronics and in nonlinear optical regime.