Defect manipulations in the quaternary semiconductor Y2Ti2O5S2: The DFT insights

Abstract

Oxysulfide semiconductor Y2Ti2O5S2 (YTOS) is a new kind of narrow band gap photocatalyst for water splitting in the range of visible light. However, it suffers from rapid electron-hole recombination and sluggish surface reaction, possibly due to unknown intrinsic defect properties. Here, we use an algorithm involving chemical potentials to investigate intrinsic defects in YTOS, and directly reveal the primary formation of antisites and anion vacancies under experimentally favorable conditions. In particular, oxygen vacancy (VO) in YTOS causes a large difference in effective mass between electron and hole, and improves the carrier separation efficiency. The change of VO concentration can further enhance the visible light absorption. This work discovers the role of defects in affecting electron-hole separation at the atomic level, and provides new opportunities for achieving highly efficient water splitting performances.