Density Functional Characterization of the Electronic Structure and Optical Properties of N-Doped, La-Doped, and N/La-Codoped SrTiO₃

Abstract

We studied the electronic and optical properties of N-doped, La-doped, and N/La-codoped SrTiO3 by means of first-principles DFT calculations to explore the physical and chemical origin of the photocatalytic activity of these structures under visible light. Our results indicate that the introduction of La into SrTiO3 lattice is in favor of the incorporation of N and reduces the formation of oxygen vacancies in N/La-codoped SrTiO3 with La at Sr site, which is the most favorable structure with respect to both energetic and activity. In the codoped configuration, N 2p states are passivated and strongly mix with the O 2p valence band edge leading to a narrowed band gap, moreover, without the presence of recombination center due to donor−acceptor pair recombination. The narrowed band gap and absence of recombination center can give a reasonable explanation for the high photocatalytic activity of N/La-codoped SrTiO3 under visible light. This charge-compensated n-type/p-type dopants codoping method should be applicable for exploiting other efficient visible light-driven photocatalysts with wide band gap semiconductors.