E-Mail Scientists have uncovered the exact mechanism that causes new solar cells to break down, and suggest a potential solution. Solar cells harness energy from the Sun and provide an alternative to non-renewable energy sources like fossil fuels. However, they face challenges from costly manufacturing processes and poor efficiency - the amount of sunlight converted to useable energy. Perovskites are materials developed for next-generation solar cells. Although perovskites are more flexible cheaper to make than traditional silicon-based solar panels and deliver similar efficiency, perovskites contain toxic lead substances. Versions of perovskites using alternatives to lead are therefore being investigated. Versions using tin instead of lead show promise but degrade quickly. Now, researchers at Imperial and the University of Bath have shown how these perovskites degrade to tin iodide, which, when exposed to moisture and oxygen, forms iodine. This iodine then helps form more tin iodide, causing cyclic degradation.