Sodium Alginate as a Natural Substrate for Efficient and Sustainable Organic Solar Cells

Organic electronics, in particular organic photovoltaics, have gained widespread attention due to their unique properties such as lightness, flexibility, and low cost. Thanks to some recent breakthroughs in organic solar cells (OSCs) that exhibit power conversion efficiencies (PCEs) approaching 20%, this technology is slowly making its way into the market as a complementary solution to conventional photovoltaic devices. OSCs are well suited for high-end smart applications, ranging from building integration and Internet of Things to consumer electronics. However, up to now, little attention has been devoted to the environmental impact and sustainability of components and processes. It is thus necessary to develop a new generation of eco-designed devices without losing the level of performance. In this work, we report the fabrication of efficient and stable solution-processed OSCs built on a free-standing sodium alginate (SA) substrate. SA is a natural biodegradable polymer derived from brown algae. It is low-cost, nontoxic, abundant, water-processable, and easy to manipulate for the realization of homogeneous and transparent foils. SA-based OSCs exhibit PCEs from 1.8 to 7.2% and can be disassembled through a safe and sustainable biocatalyzed process, allowing selective and almost entire recovery of precious metals, such as Au and Ag, as well as the separation of all of the main components. This allows us to minimize the production of e-waste, in accordance with the requirements of sustainability and the circular economy.