Highly efficient photoanodes for dye solar cells with a hierarchical meso-ordered structure.

An engineered bi-layered photoelectrode for dye solar cells has been developed which profitably employs two synergistic meso-ordered components, namely a thin meso-ordered TiO2 film and a main microparticles-based photoelectrode. The former has been deposited as an interfacial layer at the FTO-coated substrate and suppresses the back-transport reaction by blocking direct contact between the electrolyte and conductive oxide. The latter is made of hierarchical micro- and nano-structured building blocks prepared by template synthesis, which permits efficient light scattering without sacrificing the internal surface area. The optimization of light harvesting and charge recombination dynamics allowed us to achieve as high energy conversion efficiency as 9.7%.