Biosourced Hydrogel Electrolytes for Aqueous Solar Cells

Dye-sensitized solar cells (DSSCs) with water-based electrolytes are considered as one of the possible breakthrough towards DSSCs large-scale diffusion. If opportunely developed and optimized, aqueous solar cells can be considered a truly low impact photovoltaic device and no toxic components. Moreover, the possibility of gelling the electrolyte into a polymeric matrix can reduce the leakage outside the device, thus increasing the long-term stability. Above all, bio-derived polymers appear promising being renewable and easy available with low cost. In this contribution, the investigation on novel bio-derived hydrogel electrolytes for dye-sensitized solar cells is discussed and thoroughly investigated by means of physico-chemical and electrochemical characterisation. Different aqueous electrolytes gelled with carboxymethylcellulose (Na-CMC) or xanthan gum have been prepared with both I-/I3- and Co2+/3+ redox mediators. These gelled systems show good photovoltaic performances, maintaining over 90% efficiency of liquid DSSCs, as well as enhanced long-term stability. These evidences confirm that gelation with low-cost bio-derived polymers is a good strategy to improve the stability of liquid electrolytes, without compromising the overall efficiency. In addition, the use of design of experiments (DoE) is demonstrated to be a useful chemometric technique for the concurrent investigation of a series of experimental factors that directly influence the photovoltaic performances of solar cells. Results obtained enlighten that a solid mathematical-statistical approach is fundamental to support the researchers and effectively drive the experiments towards the achievements of optimal operating conditions for aqueous solar cells.