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Synthetic Molecules Capture Solar Energy

Posted: 03/09/2006

A leaf is a highly efficient solar cell and researchers in Sydney have created molecules that mimic those in plants. Like the cells in plants, they harvest light and create power. According to the research team, led by Dr Deanna D'Alessandro, the best leaves can harvest 30 to 40 per cent of the light falling on them. The latest state of the art solar cells are only 15 to 20 per cent efficient, and expensive to make. But the researchers say they have recreated some of the key systems that plants use in photosynthesis.

Bacteria and green plants use photosynthesis to convert light energy into usable chemical energy. Wheel-shaped arrays of molecules called porphyrins, collect light and transfer it to the hub where chemical reactions use the light energy to convert carbon dioxide into energy-rich sugar and oxygen. This process, which occurs in about 40 trillionths of a second, is fundamental to photosynthesis and is at the base of the food chain for almost all life on Earth.

More than 100 of the newly constructed synthetic porphyrins can be assembled around a tree-like core called a dendrimer to mimic the wheel-shaped arrangement in natural photosynthetic systems. The molecules designed by the team are about one trillionth the size of a soccer ball. But the large number of porphyrins in a single molecule means that a significant amount of light can be captured and converted to electrical energy – just like in nature.

Since they are so efficient at storing energy, D'Alessandro believes they could also be used as batteries – replacing the metal-based batteries that high technology devices depend on. The team say their preliminary results are very promising, although they are still in the early stages of building practical solar energy devices using the molecules.

Now they’ve made the molecules, the team along with their Japanese collaborators at Osaka University are working to combine them in the equivalent of a plant cell. Over the next five years they will attempt to scale the technology up to commercial scale solar panels.

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