Water-based solar cells: electrochemical behavior of state-of-art electrodes and electrolytes

Photovoltaic (PV) technology has evolved rapidly in the past few decades and now encompasses a large variety of materials and device structures (electrodes, electrolytes and coatings). A key aspect to be considered in any PV technology is the operational durability under real outdoor conditions, as well as the sustainability of materials/components and the facile integration with energy storage systems. In the last five years, dye-sensitized solar cells (DSSCs) with water-based electrolytes have been considered as one of the possible breakthroughs towards DSSCs large-scale diffusion. If opportunely developed and optimized, aqueous solar cells can be truly considered as zero-impact photovoltaic devices fabricated with non-toxic components. We show here the possibility of jellying the electrolyte into a solid matrix to boost stability, the possible use of different redox mediators solvated by water, the formulation of TiO2 pastes for screen-printable photoanodes operating in water, and the replacement of Pt cathodes with more sustainable alternatives. Overall, we will show how much water-based photovoltaics represents a challenging topic in the current energy scenario, and how it will be able to provide safe, sustainable and easily processable solar cells for building-integrated photovoltaics and portable electronics. Also, the very recent scenario integrating sustainable photovoltaics with electrochemical nitrogen reduction for ammonia production will be highlighted.