Impact of nanoparticles preparation method on the synergic effect in anatase/rutile mixtures

Abstract

The synergic effect observed in dye sensitized TiO2 solar cells cannot be explained simply by the proportion of rutile and anatase nanoparticles in the mesoporous electrode. In fact, subtle differences in the surface chemical composition dramatically influence the adsorption of N719 dye and increase by an order of magnitude the conductivity of sol-gel rutile, enhancing DSSC's efficiency. However, the now similar conductivity of rutile and anatase nanoparticles also changed the charge diffusion mechanism because electrons can flow through both materials avoiding the formation of preferential anatase channels. As a consequence, no maximum was observed in the Dnvs %rutile plot, and η and JSC become a linear function of %rutile been proportional to the flux of photoinjected electrons, or in other words to the surface concentration of N719 ruthenium dye. All those features increased the photoexcited electron lifetime, particularly around 90%rutile in homogeneous mixtures, suggesting a new synergic effect in mixed phase materials for photocatalytic applications.