Alternative energy sources, such as solar power and wind power, have received increasing attention over the past decades in order to replace the environmentally damaging and diminishing fossil fuels. Solar power is obviously one of the most attractive renewable energy sources. Up to now, the main photovoltaic (PV) devices have been based on solidstate junctions, usually made of silicon, and take advantage of the development of the semiconductor industry. A challenging new generation of solar cells is now emerging based on interpenetrating networks built from nanocrystalline sensitized oxides and conducting electrolytes. The so-called dye-sensitized solar cells (DSSCs), which use a liquid electrolyte associated with a redox couple, are easy to fabricate and lead to low-cost devices. Therefore, DSSCs constitute a promising alternative to silicon-based p-n junction PV devices. In solar cells that contain TiO 2 as a semiconductor, ruthenium-based complexes as a dye, and an iodide/iodine redox couple in acetonitrile as an electrolyte, excellent solar energy conversion performance is achieved (> 10 %).[1] Even though Grätzel's cells are now commercially available, market expansion is limited because of the use of a liquid electrolyte. Indeed, technological fabrication issues of cell sealing, handling, and maintenance, and the difficulty of marketing flexible PV cells with highly corrosive liquid electrolytes, are still of concern. A large number of alternative solutions have been proposed. These include replacement of the liquid redox electrolyte with i) ionically conductive gels, [2] ii) p-type inorganic materials such as CuI [3] and CuSCN, [4] and iii) molecular or macromolecular organic hole conductors such as triphenyldiamine, polypyrrole, [5] and p-phenylene vinylene based copolymers, [6] or substituted polythiophenes. [7] This third generation of all-solid-state PV cells is very promising and highly attractive. Overall efficiencies up to 4 % have been obtained for p-type inorganic materials [8] and up to 2.6 % for molecular organic hole-conducting materials. [9] Nevertheless, all these promising devices still exhibit poor long-term stability. This paper focuses on the sol-gel elaboration of homogeneous nanoporous TiO 2 films in which control of the architecture, porosity, and layer thickness allows optimization of the solid solar-cell efficiency and stability. A very effective design and processing of all-solid-state solar cells using high-quality TiO 2 -based mesoporous films as an n-type semiconductor layer, a Ru-based complex (Ru-dye) for visible-light absorption, [10] and regioregular poly(3-octylthiophene) (P3OT) as a hole conductor [7a,7b,11] is reported. A high current-density value and an unexpected solar-conversion efficiency (up to 3.90 mA cm -2 and 1.3 %, respectively) can be achieved, as well as a very robust device at a low cost. More than 60 cells were prepared and tested at the same time and reproducible results have been obtained. As a result, the industrial production of such solar cells has tr...

Nanocrystalline mesostructured porous titania thin films with optimized coating and thermal curing conditions have been prepared for the first time using spin-coating deposition technique. The X-ray diffraction (XRD) and the grazing incidence small-angle X-ray scattering (GI-SAXS) measurements revealed that the crystallization and diffuse sintering of amorphous TiO2 into anatase are simultaneously starting between 400 and 500 °C curing temperature, leading to a gridlike open-pore-shape transformation. The environmental ellipsometric porosimetry (EEP) measurements show that the 550 °C-cured TiO2 films exhibit a high porous volume (0.30 cm3 g-1), a large surface area (172 m2 cm-3), and a Young modulus of 1.05 GPa. All solid-state dye-sensitized solar cells (DSSC) based on nanocrystalline mesostructured TiO2 films and poly(3-octylthiophene) as hole conductor allow reproducible achievement of energy conversion efficiencies of about 0.52%. These values, obtained with thin TiO2 films (250 nm), are very promising.