Electronic structure and optical properties of K2Ti6O13 doped with transition metal Fe or Ag

Abstract

Based on the experimental study of the optical properties of K2Ti6O13 doped with Fe or Ag, their electronic structures and optical properties are studied by the first-principles method based on the density functional theory (DFT). The calculated optical properties are consistent with the experiment results. K2Ti6O13 doped with substitutional Fe or Ag has isolated impurity bands mainly stemming from the hybridization by the Fe 3d states or Ag 4d states with Ti 3d states and O 2p states and the band gap becomes narrower, the absorption edge of K2Ti6O13 thus has a clear red shift and the absorption of visible light can be realized after doping. For Fe-doped K2Ti6O13, the impurity bands are in the middle of the band gap, suggesting that they can be used as a bridge for valence band electrons transition to the conduction band. For Ag-doped K2Ti6O13, the impurity bands form a shallow acceptor above the valence band and can reduce the recombination rate of photoexcited carriers. The experimental and calculated results are significant for the development of K2Ti6O13 materials that have absorption under visible light.