Photoelectrochemical Properties of Dye-Sensitized Solar Cells based on TiO2 Nanoparticles/Nanoribbons
In this work, we have studied the influence of TiO2 morphology on the photovoltaic performances of dye sensitized solar cells (DSSCs), and electrochemical impedance spectroscopy was used to elucidate the phenomena of charge transfer and electron transport in the cells.Two photoanode types were developed by the deposition of TiO2 porous films on FTO substrate using Doctor Blade method. The first photoanode is composed of 100% (NP100) anatase nanoparticles, and the second consists of 90% nanoparticles and 10% rutile nanoribbons (NP90). SEM observations of the photoanodes revealed a high porosity of the deposited TiO2 films, which is suitable for the adsorption of large amounts of the dye. UV-Vis spectra confirmed SEM results, by displaying a strong absorption in the visible region, after the sensitization of the photoanodes in the N719 dye. Current-voltage measurements showed that the NP100 cell exhibits the best photovoltaic performances with Voc = 0.686 V, Jsc = 10.477 mA / cm2, FF = 69.17 % and η = 4.915 %. When introducing 10% of nanoribbons in the film composition (NP90 cell), the cell efficiency drops by 36.17 % mainly due to the sharp decrease in Jsc from 10.477 à 7.012 mA/cm2. It appears that adding nanoribbons which are much larger than nanoparticles significantly reduces the surface area of the TiO2 film. Moreover, EIS results showed that TiO2 nanoribbons are not beneficial to reduce interface charge recombination and did not improve the electron transport properties of the cells.
Keywords - TiO2, Nanoparticles, Nanoribbons, Dye-Sensitized Solar Cells, EIS