Design of oxide structured films for dye-sensitized photovoltaic solar cells

We have investigated a large variety of ZnO structures prepared by sol-gel, electrodeposition and occlusion electrolysis for dye-sensitized solar cell (DSSC) application. The micro-/nanostructures include (nano) porous films, nanowire arrays and hierarchical structures. Several dyes (D149, D205, N719, Z907) have been tested. We have found that the best system is the nanoporous ZnO film prepared by electrodeposition using EY as a structure directing agent and sensitized by the D149 indoline dye in the presence of octanoic acid. Electrochemical impedance spectroscopy (EIS) investigation of the cells' functioning shows a high charge collection efficiency of the ZnO-based photoelectrodes (>92%). Combined with IPCE measurements, we conclude to a high charge injection efficiency (>95%). However, the cell optimizing must now focus on the light harvesting efficiency that must be increased by broadening the sunlight wavelength range collected at the ZnO-based photoelectrode.