Electronic Structure and Optical Properties of K2Ti6O13 Doped with Transition Metal Fe or Ag

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.