Preparation of polyvinylpyrrolidone-based polymer electrolytes and their application by in-situ gelation in dye-sensitized solar cells

Polyvinylpyrrolidone (PVP), as a nitrogen-containing heterocyclic polymer, is a promising candidate for preparation of high performance iodide-based polymer electrolytes for dye-sensitized solar cells (DSSCs). In the present investigation, PVP electrolytes composed of different wt% loadings of potassium iodide and iodine were prepared, thoroughly characterized, and applied to DSSCs. The TiO2 electrode of the solid state DSSCs was optimized (film thickness, dye loading, TiCl4 treatment), to achieve high energy conversion efficiency. Differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, electrochemical impedance spectroscopy, linear sweep voltammetry, and ultraviolet-visible spectroscopy were used to characterize the PVP electrolytes. One-diode model equivalent circuit analysis was applied to DSSCs characteristic curve, in order to calculate the key electrical circuit elements values, determining solar cells efficiency. The maximum energy conversion efficiency attained by the solid state DSSCs under real test conditions was 3.74%, at about 1000 W/m2 irradiation intensity. By in-situ gelation of the PVP electrolytes onto TiO2, an optimal electrode film thickness on the order of 15 μm was achieved, which is very close to the corresponding value usually attained to liquid state DSSCs. The results are satisfactory compared to DSSCs employing liquid state factory available electrolytes, while simultaneously the PVP electrolytes preparation is simple and of low-cost, having great prospects for further optimization.