A Sustainable Hydrogel-Based Dye-Sensitized Solar Cell Coupled to an Integrated Supercapacitor for Direct Indoor Light-Energy Storage

The rapid growth of the Internet of Things ecosystem has increased the need for sustainable, cost-effective energy sources for indoor low-power devices. Indoor photovoltaics offer a solution by harnessing ambient indoor lighting, with dye-sensitized solar cells (DSSCs) emerging as strong candidates for these applications. When it comes to indoor environments, there is an increased demand for nontoxic and nonflammable solvents for electrolytes. The use of water-based electrolytes is a promising way to address these issues, while ensuring the eco-friendliness and sustainability of these devices. Herein, a DSSC system is employed featuring an aqueous gel electrolyte composed of xanthan gum, a biosourced polymer, and an iodide/triiodide redox couple. The performances of the cells are characterized under LED lighting, reaching efficiencies up to 3.5% in indoor conditions, and then integrated with an electric double-layer capacitor, also based on a xanthan gum gel electrolyte, resulting in a fully aqueous device for indoor light-energy harvesting and storage with an overall photoelectric conversion and storage efficiency of 1.45%.