Visualizing charge transfer and structural change at dye-nanoparticle interface

Dye molecules (or sensitizers) adsorbed onto highly porous nanocrystalline electrode are the key elements in a dye sensitized solar cell (DSSC). Determining electron/energy transfers coupled with structural changes at dye-nanoparticle interface is essential in understanding the fundamental mechanism, and therefore, realizing the rational designs of solar cells. Laser-initiated time-resolved X-ray absorption spectroscopy (LITR-XAS) has been used to probe the electron/charge transfer and structural changes at dye-nanoparticle interface. The photoexcited RuN3 molecules inject electrons to TiO2 semiconductors and form RuN3 cations, which have been visualized by LITR-XANES and XAFS spectra measured at Ruthenium K-edge at different delay times relative to the laser excitation. The time evolution of the Ru oxidation state and intranuclear distance in RuN3 complex has been detected. These measurements demonstrate a significant potential o f using LITR-XAS to study the interfacial phenomena at surface of nanomaterials in solar fuel generation.