Nano-flake structure boosts solar cell performance

Nano-flake structure boosts solar cell performance

A new nanostructure shape called nano flakes and being developed in Denmark could cut the cost and improve the efficiency of solar cells, bringing solar power within the grasp of ordinary households.

Less than one percent of the world’s electricity currently comes from the sun because it is difficult to transform solar energy into electricity. But a discovery at the University of Copenhagen in Denmark may offer a major step forward towards boosting the exploitation of solar energy.

During work on his doctoral thesis at the Nano-Science Center and the Niels Bohr Institute at the University of Copenhagen, researcher Martin Aagesen found a new and untried material. “I discovered a perfect crystalline structure. That is a very rare sight. While being a perfect crystalline structure we could see that it also absorbed all light. It could become the perfect solar cell,” he explains.

“I believe nano flakes have the potential to convert up to 30% of solar energy into electricity – twice the amount achieved currently – because they reduce the distance energy has to travel in the cell and thus lessen the loss of energy. These cells would also use smaller amounts of semiconducting silicon, making them less expensive than the photovoltaic (PV) cells currently available.”

The new semiconductor nanostructure is being developed to produce a particularly effective solar cell by SunFlake – a science spinout company from the Nano-Science Center with Dr Aagesen as chief executive officer (CEO). The large surface-to-volume ratio of the developed nanostructures as well as the texture of the covered surface allows a high absorption coefficient of the incoming sunlight without the use of an antireflective layer. The resulting elements would require far fewer complicated, time-consuming and expensive processing steps than existing materials.

Control of nanostructures makes it possible to combine different semiconductor materials since requirements such as the need for a similar crystal structure to the carrier substrate is relaxed. The only purposes for the carrier substrate are to allow for the growth of the nanostructures and to act as a contact to the light-absorbing nanostructures when the solar cell is operating. This advantage could influence the cost of the final solar cell dramatically since only minute amounts of expensive ultra clean material is needed, compared with current state-of-the-art silicon solar cells today.

SunFlake is one of the first companies to use nanostructures as the only active element in a solar cell. The prospect of achieving record high conversion efficiencies combined with a reduction in fabrication cost could give SunFlake a strategic advantage in the fast growing and highly competitive photovoltaic market. Initial funding in 2007 came from the University of Copenhagen and Danish venture capital fund SEED Capital.