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

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 N-2 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 (eta) and short circuit density (J(sc)) for TiO2 (amb) were 1.90 % and 5 mA/cm(2) respectively, while the TiO2 (press) cell exhibited a 40 and 50 % increase in J(sc) and eta values respectively. This was correlated with increased dye loading capacities due to a broader distribution of pore size towards the mesopore region.