https://phys.org/news/2018-06-sea-urchin-skeleton-solar-cell.html

Noorduin converts calcium carbonate structures such as a sea urchin skeleton into perovskite, a highly promising novel material for solar cells. "In effect, this is alchemy," says Noorduin. "Midas changed everything into gold, and we are now changing calcium carbonate into perovskite."

Calcium carbonate is highly abundant on Earth, and can be found in chalk mines and animal skeletons, for example. Noorduin had previously found a way of making a range of microstructures from calcium in order to understand how nature does it. But the material has few applications. Perovskite, however, offers more possibilities, and it is a highly promising novel material for solar cells. Solar cells produced from the semiconductor perovskite are more efficient and cheaper than traditional silicon solar cells. They are also the subject of increasing amounts of research. "By converting a predetermined structure of calcium carbonate into the functional perovskite, we now have control over both the shape and function of the material," says Noorduin.