Biomineral-inspired mechanically tough perovskite solar cells with enhanced stability

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Perovskite solar cells (PSCs) are solution processable, have high efficiencies and promise low cost renewable electricity. Unfortunately, the widespread application of PSCs is being held back by their poor long-term stability. Their established rivals, crystalline-silicon solar cells, offer a 25 year operational lifetime. However, high efficiency PSCs are operationally stable for less than 6 months. Perovskites have very low mechanical toughness due to the intrinsically low energy required to separate perovskite crystals. Solar cell operation lifetime increases with mechanical toughness and we aim to exploit this relationship to greatly enhance the stability of high efficiency PSCs. Taking inspiration from highly tough natural biomaterials (such as nacre) we will use synthetic analogues of adhesive proteins to glue the crystals together and increase perovskite mechanical toughness. Our new particles are ultra-deformable nanometre-sized gel particles (termed ultra-low crosslinked nanogels, ULC nanogels). Building on our earlier work where conventional nanogels improved lead-PSC stability, novel ULC nanogels will be prepared that conformally coat and interlink perovskite crystals. They will flatten to become ultra-thin and allow charges to move unhindered between crystals. We will also study lead-free, tin-perovskites and increase their operational stability by a combination of improvements in chemical stability and mechanical toughness. The link between the mechanical toughness and PSC stability will be investigated experimentally and using state-of-the-art modelling techniques. Modelling will also be used to study the energy changes involved in chemical degradation so as to establish materials design rules for PSCs with enhanced stability. A successful outcome to this project would provide improved fundamental understanding of the interplay between perovskite mechanical toughness and stability as well as a high efficiency demonstrator(s) with a projected operation lifetime of 8 years. Such a result would bring the large-scale deployment of perovskite photovoltaics for CO2-free electricity generation closer and increase energy security.