Optical pump — THz probe studies of size-dependent ultrafast charge carrier dynamics in WO3 particles for photoelectrochemical cells

Terahertz (THz) spectroscopy is an excellent non-contact electrical probe of charge injection and conductivity with sub-picosecond time resolution. One may exploit this capability to study a variety of materials, and here we choose to probe the transient photoconductivity of tungsten (VI) oxide (WO
₃
), a wide band gap metal oxide. This semiconductor is of interest in renewable energy research and artificial photosynthesis because it can be used as the photoanode in photoelectrochemical cells. The ultrafast charge carrier dynamics on the picosecond timescale have yet to be investigated by any technique, let alone THz spectroscopy. Our particular interest is in the characterization and dynamics of photoinduced charge carriers that are required for efficient oxidation at the metal oxide/electrolyte interface.