Unveiling charge dynamics of visible light absorbing oxysulfide for efficient overall water splitting

Oxysulfide semiconductor, Y2Ti2O5S2 , has recently discovered its exciting potential for visible-light-induced overall water splitting, and therefore, imperatively requires the probing of unknown fundamental charge loss pathways to engineer the photoactivity enhancement. Herein, transient diffuse reflectance spectroscopy measurements are coupled with theoretical calculations to unveil the nanosecond to microsecond time range dynamics of the photogenerated charge carriers. In early nanosecond range, the pump-fluence-dependent decay dynamics of the absorption signal is originated from the bimolecular recombination of mobile charge carriers, in contrast, the power-law decay kinetics in late microsecond range is dominated by hole detrapping from exponential tail trap states of valence band. A well-calibrated theoretical model estimates various efficiency limiting material parameters like recombination rate constant, n-type doping density and tail-states parameters. Compared to metal oxides, longer effective carrier lifetime similar to 6 ns is demonstrated. Different design routes are proposed to realize efficiency beyond 10% for commercial solar-to-hydrogen production from oxysulfide photocatalysts.

Automated summary

The study examines the dynamics of photogenerated charge carriers in the oxysulfide semiconductor Y2Ti2O5S2 through transient diffuse reflectance spectroscopy measurements and theoretical calculations, revealing potential for visible-light-induced overall water splitting. Various efficiency limiting material parameters are estimated, with proposed design routes to achieve efficiency beyond 10% for commercial solar-to-hydrogen production from oxysulfide photocatalysts. Longer effective carrier lifetime is demonstrated compared to metal oxides.