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 (Jsc) for TiO2 amb were 1.90 % and 5 mA/cm2 respectively, while the TiO2 press cell exhibited a 40 and 50 % increase in Jsc and η values respectively. This was correlated with increased dye loading capacities due to a broader distribution of pore size towards the mesopore region.