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Geometric pattern captures more light in organic solar cells

Geometric pattern captures more light in organic solar cells
McCormick researchers have designed a geometrically-patterned light scattering layer that could make solar cells more efficient and less expensive. Image from Northwestern University.

Researchers at Northwestern University are using geometry to redesign the layers of organic solar cells, increasing the amount of sunlight captured and converted to power.

The researchers played around with different geometric patterns in the scattering layer of an organic solar cell to maximize the amount of time light remains trapped within.

“We wanted to determine the geometry for the scattering 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. “But with so many possibilities, it’s difficult to know where to start, so we looked to laws of natural selection to guide us.”

What the researchers did was develop a mathematical search algorithm based on natural evolution that found a specific geometrical pattern optimal for capturing light.

They began with dozens of random design elements, then “mated” and analyzed the offspring for their light-trapping capabilities. This process was carried out over more than 20 generations and also accounted for evolutionary principles of crossover and genetic mutation.

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

The pattern is set to be fabricated with partners at Argonne National Laboratory. This could allow for more efficient, less expensive solar power as organic solar cells are cheaper to manufacturer then silicon-based solar cells.

Mr. Sun worked on the design with Wei Chen, Wilson-Cook Professor in engineering Design and a professor of mechanical engineering at McCormick, and Chen Wang and Shuangcheng Yu, graduate students at the department of mechanical engineering. – EcoSeed Staff

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