New pattern to maximise solar energy

WASHINGTON, USA: Researchers have come up with a new pattern for organic solar cells that could ensure more efficient and low cost solar power.

Researchers at Northwestern University sought to design the geometric pattern of the current single-crystal silicon solar cells to maximize the amount of the time light remained trapped within the cell instead of trying to raise the efficiency by altering the thickness of the solar cell's polymer layer.

Using a mathematical search algorithm based on natural evolution, the researchers pinpointed a specific geometrical pattern that is optimal for capturing and holding light in thin-cell organic solar cells, according to a Northwestern statement.

The resulting design exhibited a three-fold increase over the Yablonovitch Limit, a thermodynamic limit developed in the 1980s that statistically describes how long a photon can be trapped in a semiconductor.

"We wanted to determine the geometry for the scattering (solar cells) layer that would give us optimal performance," said Cheng Sun, assistant professor of mechanical engineering in Northwestern's McCormick School of Engineering and Applied Science in Evanston, Illinois, and study co-author.

Researchers began with dozens of random design elements, then "mated" and analysed their offspring to determine their particular light-trapping performance.

This process was carried out over more than 20 generations and also accounted for evolutionary principles of crossover and genetic mutation.

The resulting pattern will be fabricated with partners at Argonne National Laboratory.