Codoping synergistic effects in N-doped SrTiO3 for higher energy conversion efficiency

Abstract

To understand the codoping synergistic effects in metal oxide semiconductors with wide band gaps as photocatalysts, we chose N-doped SrTiO₃ as a host to determine the effects of some nonmetal and metal codopants on it by performing the first-principles calculations for N/H-, N/X- (X = F, Cl, Br, I), N/M₁- (M₁ = V, Nb, Ta) and N/M₂- (M₂ = Sc, Y, La) codoped SrTiO₃. Our study shows that the codoping of N with nonmetal atoms H, F and all metal atoms except Ta can reduce the energy cost of N doping and thus improve the solubility of N in SrTiO₃. Octahedra in codoped SrTiO₃ suffer from a relative larger distortion than that of N-doped SrTiO₃ and the distorted octahedra can generate a more efficient internal field, which can promote the separation and reduce the recombination of electron-hole pairs, due to the nonzero dipole moment of distorted octahedra. In the codoped structures, compensating vacancy defects can be avoided and narrowed band gaps without recombination centers (oxygen vacancies) can be realized (except the N/Sc-codoped SrTiO₃ that shows a wider band gap than the pristine SrTiO₃). The N related defect acceptor can be passivated resulting from electron transfer from donor to acceptor (DAP recombination). As photocatalysts, these defective-less codoped systems with narrowed band gaps should manifest high energy conversion efficiency under visible light irradiation. One should consider this passivated donor/acceptor dopants–codoping approach for exploiting new available visible light-driven photocatalysts.