A study on the microstructural development of gel polymer electrolytes and different imidazolium-based ionic liquids for dye-sensitized solar cells

Quasi-solid state electrolyte (gel-like) based on polymer matrix PVDF-HFP/PEO is considered as a suitable candidate for producing DSSC due to its essential influence on the performance of the device. In this work, PVDF-HFP/PEO membranes were prepared over the whole composition range in presence of either one of the ionic liquids (ILs) including BMII plus LiI, or BMIMBF4 via phase inversion and compared with liquid electrolyte and ILs individually. It was found that the blend ratio affected some of the membrane properties, such as porosity, pore size, pore connectivity, liquid uptake ability, and morphology. SEM analysis and mercury porosimetry were used to study the pore configuration and porosity of the membranes. The effects of two semicrystalline polymers on the morphology and crystallinity of the membrane were examined by DSC and also WAXD. It was found that there is a direct relationship between the crystallinity reduction and improvement of ionic conductivity of the samples. The photovoltaic performances of the fabricated DSSC at the highest ionic conductive optimized membrane revealed an improvement of Voc, Jsc, fill factor, and the solar conversion efficiency of 6.47%. The long-term durability of the quasi solid DSSC was increased compared to a liquid type electrolyte.