Charge carrier mapping for Z-scheme photocatalytic water-splitting sheet via categorization of microscopic time-resolved image sequences.

Photocatalytic water splitting system using particulate semiconductor materials is a promising strategy for converting solar energy into hydrogen and oxygen. In particular, visible-light-driven 'Z-scheme' printable photocatalyst sheets are cost-effective and scalable. However, little is known about the fundamental photophysical processes, which are key to explaining and promoting the photoactivity.

Lifetime mapping of photo-excited charge carriers by the transient grating imaging technique for nano-particulate semiconductor films.

The transient grating (TG) imaging technique has been developed, where the refractive index change due to the photoexcited charge carriers excited with a stripe patterned light can be visualized. The spatiotemporal imaging of photoexcited charge carriers was demonstrated for a nanoparticulate TiO film. In the analytical procedures to map out the time constant distribution, the averaged response of photoexcited carriers in each image was obtained from the Fourier transform of the TG images since the image has a spatial modulation with a stripe pattern of light.