Titanium Grids and Polymer Electrolytes for Flexible Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) gather great interest for the possibility of different applications such as architectural integration, wearable photovoltaics and supply systems for low power electronics. For the development of flexible devices some critical issues still have to be solved, such as the use of solid or quasi-solid electrolytes and convenient sealing materials for the packaging, able to provide satisfactory duration in time. This work presents the results obtained on a flexible DSSC, fabricated in our lab using UV-crosslinked polymeric membrane as electrolyte and titanium grids both as the anode and as the cathode substrate. The Ti grid was vertically dipped into a diluted TiO2 paste (18NR-AO Active Opaque, Dyesol), in order to obtain a suitable mesoporous semiconductive layer, which was subsequently annealed at 525 °C. The photoanode was then incubated into a 0.3 mM N719 dye solution (Ruthenizer 535bis-TBA, Solaronix) for 15 h. The cathode was obtained depositing a 5 nm layer of platinum by means of sputtering. Regarding the polymeric membrane, this was prepared UV-irradiating a solution of two oligomers (bisphenol A ethoxylate dimethacrylate, BEMA and poly(ethylene glycol) methyl ether methacrylate, PEGMA) and a free-radical photoinitiator. The packaging was made with two 75 μm-thick PET foils and each layer of the cell was spaced by a thermoplastic foil. The sealing was performed using a hot press set at 85 °C. Both rigid and flexible DSSC configurations have been tested by a careful characterization of their electrical performances. The small decrease in the overall efficiency of the flexible DSSC configuration with respect to the rigid one is related to the different quality of the electrodes/electrolyte interface contacts. In conclusion, the simplicity of fabrication and the relatively low cost employed materials pave the way for an industrial scale-up and a possible future commercialization.