Impact of drying procedure on the morphology and structure of TiO₂ xerogels and the performance of dye sensitized solar cells

Abstract: Different morphologies of TiO₂ photoelectrodes for dye sensitized solar cells were obtained by using TiO₂ gels dried in normal conditions (TiO₂ ^amb) and in CO₂ atmosphere at high pressure (TiO₂ ^press). After a subsequent calcination, the powders were processed as pastes and drop-casted on conductive glass in order to prepare photoanodes for dye sensitized solar cells. N719 commercial dye was used as sensitizer in all the experiments. The structure and morphology of the processed TiO₂ materials were investigated via X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N₂ adsorption/desorption measurements. The dye adsorption capacity of the photoanodes was tested using ultraviolet-visible absorption spectroscopy. The photovoltaic performances of the dye sensitized solar cells were investigated using current/voltage curves (I/V), open circuit photovoltage decay measurements and electrochemical impedance spectroscopy. The conversion efficiency (η) and short circuit density (J_sc) for TiO₂ ^amb were 1.90 % and 5 mA/cm² respectively, while the TiO₂ ^press cell exhibited a 40 and 50 % increase in J_sc and η values respectively. This was correlated with increased dye loading capacities due to a broader distribution of pore size towards the mesopore region. Graphical Abstract: [InlineMediaObject not available: see fulltext.]