US scientists use additives to improve performance of organic solar cells

Researchers at the U.S. Argonne-Northwestern Solar Energy Research Center (ANSER), a collaboration between Northwestern University and the U.S. Department of Energy’s (DOE) Argonne National Laboratory, are seeking to improve the molecular microstructures of organic solar cells by using additives.

The scientists have developed the photoactive layer of the cell from thin film, which was produced via spin coating. In the process, the material used for creating the thin film was dissolved in a solvent, on a spinning surface. This, the research group said, has enabled it to observe through an X-ray beamline how the film’s crystal structure evolves in real time.

The study, published in scientific review Advanced Materials, stresses how certain additives can considerably affect both the time it takes for the film’s structure to stop changing, and the intermediate structures the film adopts during evolution. Furthermore, it shows that films that are produced more slowly with additives, generally perform better than the more rapidly formed films.

“Producers of solar cells will often go to the next step in production quickly after spin coating, which has the potential to lock the morphology while the structure is still forming. This can significantly affect the cell’s performance, positively and negatively,” said the research coordinator Eric Manley.

More complex structures will now be analyzed, and different choices on how to improve the cells’ performance will also be taken into account, the research team concluded.