Aqueous electrolyte for DSSCs: DoE investigation on redox mediator and gelling agents

Dye sensitized solar cells (DSSCs) are a promising and interesting technology able to convert solar light into electricity and have recently achieved efficiencies up to 14%. Nevertheless DSSCs are not yet commercialized on large scale due to their issues concerning safety and long-term stability. In fact, standard high-efficiency DSSCs are prepared mainly with organic solvent-based liquid electrolytes, i.e. acetonitrile and methoxypropionitrile, and are often characterized by high vapor pressure, toxicity and flammability. In recent years, with the idea of creating efficient, safe, and low-cost DSSCs, the research moved the attention towards alternative solvent-based electrolytes. Above all, DSSCs with water-based electrolytes look like one of the best solution providing reduced costs, non-flammability, better stability, and environmental compatibility. Moreover, the possibility of gelling the liquid solvent into a polymeric matrix can reduce the electrolyte leakage outside the device, increasing the long-term stability. In this contribution, the investigation on a series of iodine-based 100% aqueous electrolytes is presented. Thanks to our knowledge and to a multivariate approach, useful to perform DoE (Design of Experiment) investigation, the effects on DSSCs performance of the change in redox mediator concentrations and in photoanode preparation are evaluated. Finally, the gelation of aqueous electrolytes with a bio-derived polymer is also studied as well as their interesting photovoltaic performances.