Hierarchical porous TiO2 and ionic liquid-like polysiloxane electrolyte for solid state-Dye-Sensitized Solar Cells

Overview & Synopsis

DSSC is a 3rd generation photovoltaic technology with potential to economically harvest and efficiently convert photons to electricity. Full solid state-DSSC based on solid polymer electrolyte prevents the solvent leaking and evaporation during cell fabrication and operation, which will effectively prolong the cell life time. However, it suffers from low ionic conductivity and poor pore infiltration.The present thesis is dedicated to the concomitant development of polysiloxane-based polymer electrolytes on one side, and TiO2 photoanodes with tuned porosity on the other side, and their incorporation in solid state dye sensitised solar cell (ss-DSSCs), with the aim to improve their photovoltaic efficiency and the long term stability. To best of our knowledge, DSSCs comprising bimodal TiO2 layers and polysiloxane electrolytes have never been reported.The ionic conductivity and tri-iodide diffusion coefficient of the polysiloxane-based poly(ionic) liquids (PILs) were largely improved by adding of ionic liquids (ILs) or ethylene carbonate (EC), achieving ionic conductivities of 10−4 -10−3 Scm−1. The DSSCs fabricated with the optimized electrolytes showed efficiencies up to 6%, with long term stability for 250 days.Bimodal TiO2 films with dual porosity (meso- and macro-porosity) were fabricated by spin-coating, by using soft and hard templating. The dual templated films benefit from increased pore size while maintaining high surface area for dye adsorption. Bimodal films were shown to be more efficient when tested with polymer electrolytes, having comparable efficiencies with liquid electrolyte when in DSSCs, despite lower dye uptake.This thesis brings a significant contribution to the field of DSSCs as efficient and stable solar cells were prepared from newly synthesized polymer electrolytes and bimodal films.