Chlorophyll inspires Aussies in quest for green power

Seeking efficient solar cells

Researchers in Australia have developed technology that could pave the way for highly efficient solar cells.

The team, from the Molecular Electronics Group at the University of Sydney, has created molecules that mimic the systems plants use for photosynthesis.

Researcher Deanna D'Alessandro explains the botanical inspiration for the work, describing leaves as "amazingly cheap and efficient solar cells".

"The best leaves can harvest 30 to 40 per cent of the light falling on them," she says. "The best solar cells we can build are between 15 and 20 per cent efficient, and expensive to make."

During photosynthesis (a process by which plants convert sunlight into useable chemical energy) light is collected by wheel-shaped arrays of molecules called porphyrins. Porphyrins are ring-shaped organic molecules. Chlorophyll is essentially a porphyrin surrounding a central magnesium ion.

Chlorophyll is the green pigment in plants responsible for absorbing energy from sunlight. A complex series of reactions in the leaf then uses this energy to transfer electrons from water to carbon dioxide, forming sugar along the way, with oxygen as a by-product. The porphyrin ring is the principal structure in capturing the energy.

"We have been able to construct synthetic porphyrins," D'Alessandro explains. "More than 100 of them can be assembled around a tree-like core called a dendrimer to mimic the wheel-shaped arrangement in natural photosynthetic systems.

"Since they are so efficient at storing energy, we think they could also be used as batteries, replacing the metal-based batteries that our high technology devices depend on today," she adds.

Although the work is still at an early stage, the team is optimistic about its potential.

The researchers are now working with collaborators at Osaka University to combine them into a synthetic equivalent of a plant cell. If this stage is successful, they plan to scale up the technology to commercial scale solar panels over the next five years. ®

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