TiO2 mesoporous thin films acting as photoelectrode in dye-sensitized solar cells

This study aims at developing thin films of nanocrystalline, mesostructured titanium dioxide in order to build low cost and efficient photovoltaic devices.
The synthesis is based on the Evaporation Induced-Self Assembly method using titanium isopropoxide as inorganic source, block copolymers as structuring and porogeneous agents and ethanol as solvent. The films were obtained by dip-coating various substrates in the solution.
The influence of different experimental parameters, such as dip-coating and ageing relative humidity, withdrawal speed, surfactant:Ti ratio, substrate, was studied.
The post-deposition thermal treatment had to be accurately adjusted in order to maximise the crystallisation of the inorganic network while avoiding the collapse of the porous mesostructure. The final structure obtained is discussed in the light of the XRD results combined with TEM analysis.
Moreover the cell performance is limited by the film thickness which is mainly responsible of the small amount of absorbed light. Therefore a multilayer deposition process was studied and the as-obtained mesostructure was characterized by TEM, RBS and environmental ellipsometry.