Investigating the electrolyte iodine concentration effect on photovoltaic properties of dye-sensitized solar cells by electrochemical impedance spectroscopy

The purpose of this work was to investigate the effect of I2/LiI molar ratio (X) of electrolyte on photovoltaic properties of nanostructured dye sensitized solar cells (DSSCs) by a electrochemical impedance spectroscopy (EIS) method. Different X ratios, up to X=2, were investigated. Semiconducting TiO2 layer was fabricated using Pechini based TiO2 nanoparticle paste. It was observed that open circuit voltage (Voc) decreases with X, while short circuit current density (Jsc), fill factor (FF) and conversion efficiency (η) first increase and then decrease with increasing X. It was explained that these variations were due to the effect of X on kinetic parameters such as; Nernstian diffusion impedance (Rd) of I3− ions and impedances at TiO2/dye/electrolyte (RTiO2) and electrolyte/Pt (RPt) interfaces. Rd and RTiO2 decreased with X, but the curve of RPt versus X had a minimum.