Descripción del proyecto
Halide perovskites are the next big thing in solar energy. State-of-the-art perovskite solar cells outperform established technologies with the advantage of processing from solution. Solution-processed perovskite solar cells are made spraying a precursor ink onto a substrate: the perovskite forms as the chemicals contained in the ink crystallize. This production process makes halide perovskites a valid low-cost alternative established material such as silicon. Furthermore, halide perovskite can work in tandem with silicon to break the theoretical power conversion efficiency limit of 33% according to the Shockley-Queisser model.
However, the most effective photovoltaic perovskites contain more than 10% by weight of lead, which overstep the limits adopted in most of the countries to regulate the use of heavy metals in electronics.
The FREENERGY project aims at achieving efficient and cost-effective lead-free perovskites replacing lead (Pb) with tin (Sn). We have demonstrated that tin is relatively inert if dispersed in the environment as compared to lead, which is prone to enter into plants and thus into the food chain. This solution does not present any manufacturing issue, as making tin-based perovskite is very similar to make lead-based perovskite. The main obstacle is represented by the low chemical stability of Sn2+, which is very prone to be oxidized to Sn4+. We have identified three key strategies:
• Inorganic cations: We found that organic cations comprising perovskite are more prone than inorganic in to activate the Sn oxidation. We have selected a series of inorganic cations comprising Cs and K to replace the organics most commonly used.
• Alternative solvents: dimethyl sulfoxide is currently used to synthesize the perovskite, but it contributes to the oxidation. We identified alternative solvents to overcome this issue.
• Reducing additives: The perovskite materials are deposited from a solution comprising the precursor of the materials and the solvents.