From organic solvents to water: a more sustainable approach toward industrially-upscalable hybrid solar cells

Since the discovery of Dye-sensitized Solar Cells (DSCs), the scientific community has always firmly considered the presence of water in the cell, either in the electrolyte or at the electrode/electrolyte interface, strongly harmful to photovoltaic performances and long term stability. However, the idea of creating an efficient, inexpensive and environmental friendly system based on water is still attractive especially for a large scale diffusion of this technology. In recent years, an increasing number of research articles has been published in this direction and new dyes, electrodes and electrolyte components are continuously proposed. Being the initial purpose of DSCs the construction of an artificial photosynthetic system able to convert solar light into electricity, the use of water as key component may represent a great step forward to their widespread diffusion in the market. Indeed, by means of DSCs fabricated with 100% water-based electrolytes, reduced costs, non-flammability, reduced volatility, improved safety and environmental compatibility could be easily achieved. A starting point in this direction is given in this work and few peculiar and unconventional behaviors, observed in the literature and in our laboratories, are presented for truly water-based electrolytes. This contribution proposes an investigation on the stability of different classes of dyes, in a fully aqueous environment, and the effect of different aqueous electrolytes. Particularly, by means of a multivariate approach (DoE) we were able to study different kinds of aqueous electrolyte, thoroughly investigating their effect on the photovoltaic performance and stability of the resulting devices.