Tuning electrolyte configuration and composition for fiber-shaped dye-sensitized solar cell with poly(vinylidene fluoride-co-hexafluoropropylene) gel electrolyte.

Efficient energy generation device is desired to couple with soft electronics for driving devices. Due to frequent uses of soft electronics in indoor conditions, flexible fiber-shaped dye-sensitized solar cell (FDSC) is regarded as the most promising energy generation device due to high light-to-electricity conversion maintenance under weak dim light. Using gel electrolyte to assemble FDSC cannot only restrict electrolyte leakage but also improve device flexibility and stability especially under bending conditions. In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) gel electrolyte is used to fabricate FDSC composed of curled TiO2 nanotube/Ti wire photoanode and Pt counter electrode. It is the first time to control gel electrolyte configuration by adding different PVdF-HFP concentrations, and to optimize iodine concentration in electrolyte regarding to redox ability and electrolyte transmittance. Configuration of gel electrolyte is carefully analyzed to define porous layer and concrete layer of polymer for accumulating liquid electrolyte and inhibiting leakage and evaporation. The highest solar-to-electricity conversion efficiency of 6.32% is obtained for FDSC with 9% PVdF-HFP and 0.04 M I2 in electrolyte, due to well-defined cross-linking structure, abundant redox reactions, and high incident-light illumination through electrolyte. Electrochemical impedance spectroscopy and intensity-modulated photocurrent/photovoltage spectroscopy are used to analyze charge-transfer resistance and charge-collection efficiency.