Innovative and sustainable materials for aqueous dye-sensitized solar cells: a focus on photoanode/electrolyte interface

Emerging photovoltaic (PV) has evolved rapidly in the past decades and they are claiming their role as valuable alternatives to Silicon-based devices, especially for building integrated and indoor application. Among them, Dye-Sensitized Solar Cells (DSSCs) gained a leading role when diffuse and low-intensity light sources are used, approaching the Shockley-Quessier limit. Additionally, they are generally recognized as a sustainable technology. To further stress the sustainability claim and to improve the long-term stability of these device, the research recently focuses on water-based electrolytes (eventually jellified) leading to the development of aqueous DSSCs. Unfortunately, the improved sustainability is associated to lower photovoltaic performances compared to conventional devices. To improve light conversion efficiency, specifically designed materials should be designed and tested. Throughout this contribution, we summarized our recent effort in the fabrication and implementation of innovative photoanodes, electrolytes and sensitizers with a dedicated attention to the interplay between these components. Electrochemical Impedance Spectroscopy analyses allow us to highlight an unexpected behavior resulting in an additional resistance at the photoanode/electrolyte interface that could justify the lower performances of aqueous devices. 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 sustainable solar cells for building-integrated photovoltaics, indoor applications and portable electronics.