A photo-physical and electrochemical impedance spectroscopy study on the quasi-solid state dye-sensitized solar cells based on poly(vinylidene fluoride-co-hexafluoropropylene)

Quasi-solid state dye-sensitized solar cells (DSSCs) were fabricated with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) in methoxy propionitrile (MPN) as gel polymer electrolyte (GPE), tetrabutylammonium iodide (TBAI)/iodine (I₂) as redox couple, 4-tertiary butyl pyridine (TBP) as additive and silica nanoparticles as fillers. The energy conversion efficiency of the cell with 5 wt% PVDF-HFP is comparable to that one obtained in liquid electrolyte system. Solar cell containing PVDF-HFP with 0.8 M of TBAI and 0.12 M of I₂ shows maximum short-circuit current density (J_SC). Further, tertiary butyl pyridine (TBP) has little effect in improving the performance of the solar cell. Moreover, the addition of 1 wt% silica nanoparticles is found to improve the at-rest durability and the performance of the solar cell. The transient photovoltage and photocurrent measurements were employed to find out the electron lifetimes in TiO₂ electrode with different weight percentages of PVDF-HFP, various concentrations of I₂ and durability of the cell storage at 70 °C. A photocurrent density of 14.04 mA cm^-2, an open-circuit voltage of 0.71 V, a fill factor of 0.598 and an overall conversion efficiency of 5.97% under 100 mW cm^-2 was observed for the best performance of a solar cell in this work. Crown