Metal oxide-based photoanodes are critical components of dye sensitized solar cells (DSSCs), which are photoelectrochemical cells for the conversion of solar energy, promising to have several benefits as compared with their traditional counterparts. A careful engineering of the wide band gap metal oxide composing the photoanode, as well as their process design, is strategic for improving device performances and for planning a near future production scale up, especially devoted to reducing the environmental impact of the device fabrication. Herein, we present the application of ZnO hierarchical structures as efficient materials to be applied as photoanodes in DSSC, in the perspective of looking for alternative to TiO<sub>2</sub> nanoparticles, currently the most exploited metal oxide in these devices.
ZnO@SnO<sub>2</sub> multilayered network was deposited on fluorine doped tin oxide (FTO) glass and applied as photoanode in dye sensitized solar cells whose functional performances are compared with single oxide-based photoanodes made of SnO<sub>2</sub> nanoparticles and ZnO microparticles. Multi-oxide photoanodes provide for enhanced photoconversion efficiency (3.31%) as compared with bare SnO<sub>2</sub> nanoparticles (1.06%) and ZnO microparticles (1.04%). Improved functional performances of the ZnO@SnO<sub>2</sub> layered network are ascribable to partial inhibition of back electron transfer from SnO<sub>2</sub> to the redox electrolyte, guaranteed by the ZnO, which acts as a capping layer for the underlying SnO<sub>2</sub>.