Effect of casting condition on the porosity of polymer membrane and its impact on the photoelectrochemical behavior of dye-sensitized solar cells

Abstract

The present study demonstrates the effect of casting conditions (relative humidity and temperature) on morphology of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) membranes prepared from solution of the co-polymer in tetrahydrofuran (solvent) and water (non-solvent and pore former). Membranes with thicknesses of 4-6 mu m have been obtained by doctor blade casting under different conditions. High-temperature cast membranes yield less porous membranes. Low-temperature casting results in a maximum of 52 % (surface) porosity of membranes. High relative humidity (80 %) during casting results in bigger pore size in membrane than low relative humidity. Membranes containing liquid electrolyte have been subjected to testing in dye-sensitized solar cells as quasi-solid electrolytes. A maximum photo-conversion efficiency of 2.5 % for 1 cm(2) active area has been achieved in membrane-based cells as compared to 2.8 % for cells having liquid electrolyte. High-temperature cast membranes result in poor performance due to hindrance in the charge transport.