Saffron dye-sensitized solar cells with polyvinyl alcohol based gel polymer electrolytes

Gel polymer electrolytes (GPEs) based on polyvinyl alcohol consist of iodide/triiodide ions have been prepared and tested for saffron dye-sensitized solar cells (DSSCs). The effect of 4-tert-butylpyridine (TBP) on the GPE and DSSC has been investigated. The room temperature ionic conductivity of GPEs (with and without TBP) lies in the range of ~ 10^–3 S/cm and increases with increasing temperature up to ~ 10^–2 S/cm at 373 K. Current density–voltage (J–V) characteristics of DSSCs shows that the DSSC fabricated with TBP exhibits the highest short circuit current density of (2.80 ± 0.30) mA/cm² and power conversion efficiency of 0.62%. The lowest series resistance was found in the same cell's electrical impedance spectroscopy, indicating that electrolyte charge transport dominates in DSSCs. Furthermore, intensity-modulated photocurrent and intensity-modulated photovoltage spectroscopies were used to evaluate the electron transfer time constant (t_r) and electron recombination time (t_rec) of the constructed DSSCs. The most efficient DSSC (with TBP) has the shortest t_r of 0.17 s and the fastest t_rec of 0.50 s.