A Charge-Separated State that Lives for Almost a Second at a Conductive Metal Oxide Interface

Transparent conductive oxides (TCOs) are widely used commercially available materials for opto-electronic applications, yet they have received very little attention for dye-sensitization applications. Now, mesoporous thin films of conductive indium-doped tin oxide (ITO) nanocrystallites are shown to support long-lived charge separation with first-order recombination kinetics (k= 1.5 s(-1)). A layer-by-layer technique was utilized to spatially arrange redox and/or chromophoric molecular components on ITO. Spectroelectrochemical measurements demonstrated that upon light absorption, each component provided a free-energy gradient to direct electron transfer at the conductive oxide interface. The long-lived nature of the photogenerated charge separated states provide favorable conditions for photocatalytic solar fuel production. Furthermore, the first-order recombination kinetics are most ideal for the fundamental understanding of interfacial charge separation dynamics.