Mara Bruzzi, Riccardo Mori, Ennio Carnevale, Monica Scaringella and Franco Bogani
Among the numerous applications of TiO2 nanoparticles, dye sensitized solar cells (DSSC) have received a growing interest as low-cost devices for photovoltaic energy production. The improvement of their performance requires a better charge separation and collection and then a higher conductivity of the TiO2 matrix, which, being in the nanocrystalline (nc) form, is highly disordered material. It is therefore of utmost importance to determine the role of the defect distribution on the transport properties of nc-TiO2. Thermally Stimulated Currents (TSC) is a powerful technique to analyse those defects, nonetheless, a thorough model to discuss TSC emission in highly disordered materials is still lacking. Both multi-trapping and hopping conduction mechanisms should be considered in principle, but the importance of these two mechanisms is still controversial, also owing to the fact that they predict the same behaviour. Mara Bruzzi et al. (see the Invited Article on pp. 1691–1697) present a set of TSC measurements devised to elucidate the role in the TiO2 conductivity of the localized states induced by disorder. The experimental results are analysed without any a-priori assumption on the conduction mechanism, considering the two mechanisms of multi-trapping and hopping as complementary rather than alternatives.