Aqueous coating of efficient flexible TiO2 dye solar cell photoanodes

We describe the preparation and characterization of flexible TiO2 photoanodes coated on indium tin oxide–polyethylene naphthalate (ITO–PEN) substrates from aqueous solutions. We find that the use of hexafluorosalisilic acid promotes low-temperature connection of the TiO2 nanoparticles, considerably increasing the solar conversion efficiency. In addition, we report that highly dispersed TiO2 nanocrystals improve adhesion to the substrate, while micron-size aggregates improve the porosity of the photoanode. Hence, optimal results of 5% conversion efficiency at 0.5 sun are obtained by the combination of these two particle sizes.