Researchers at Northwestern University published a paper entitled “Highly Efficient Light-Trapping Structure Design Inspired by Natural Evolution,” in the journal Nature earlier this month, showing that single-crystal silicon solar cells do not have to be as expensive as they currently are.
The solution is hidden in the new geometric pattern of the scattering layer, which maximizes the amount of time light remains trapped within the cell. The team used a mathematical search algorithm to outline the specific pattern needed to capture the light and maintain it in the thin-cell organic solar cells.
They measured a three-fold increase over the thermodynamic limit developed in the 1980s, known as Yablonovitch Limit.
This is achieved through the scattering layer, which is a geometrically-patterned dielectric layer and is the first place entered by light in the solar cell. From there, the light is transmitted to the active layer, where it gets converted into electricity.
Cheng Sun, assistant professor of mechanical engineering in Northwestern’s McCormick School of Engineering and Applied Science and one of the co-author of the paper stated that this geometry gives the optimal performance. Wei Chen, another co-author and Wilson-Cook Professor in Engineering Design and professor of mechanical engineering at McCormick, explained that the geometry was determined through a genetic algorithm, which mimics the process of natural evolution, or the survival of the fittest.
To determine the geometry, the team used a dozen random design elements. They carried the process out over more than 20 generations. The fabrication of the patterns will be conducted in collaboration with the Argonne National Laboratory.