Electron transport improvement in CdSe-quantum dot solar cells using ZnO nanowires in nanoporous TiO2 formed by foam template

A facile in-situ modification of photoanode is proposed to construct a unique hierarchical TiO 2 /ZnO structure with the aim at suppressing charge recombination rate and enhancing light harvest efficiency. Foam is not only employed as the soft template to fabricate hierarchical porous TiO 2 films but also as the carrier to realize in-situ growth of one dimensional ZnO nanowires among the TiO 2 nanoparticles. The results revealed that the hierarchical porous TiO 2 nanoparticles could provide both large surface areas and suitable porosity for the loading of quantum dots. In the meantime, ZnO nanowire can act as scattering centers for light absorption and offer direct pathways for electron transportation, thus decreasing the undesired charge recombination process. Consequently, the novel ZnO nanowires in-situ modified hierarchical porous TiO 2 photoanode are used as photoanode material to boost the performances of CdSe sensitized solar cells by virtue of controlling the moderate growth of ZnO nanowires. As a result, a power conversion efficiency of 3.07% is obtained based on this modified photoanode, which manifests 39.5% improvement compared to that of the cells based on bare TiO 2 hierarchical porous films (2.20%) due to the improved interconnections between TiO 2 nanoparticles and FTO substrate caused by ZnO nanowires.