Materials that emit and manipulate light are at the heart of technologies ranging from solar energy to advanced imaging systems. But even in well-studied materials, some fundamental behaviors remain unexplained. Researchers at Rice University have now solved a long-standing mystery in a widely used organic semiconductor, revealing how tiny structural imperfections can actually improve how these materials work.

In a study published in the Journal of the American Chemical Society, the team investigated 9,10-bis(phenylethynyl)anthracene (BPEA), a model system for studying how light energy moves through materials. For years, scientists have observed unusual optical behavior in BPEA, specifically two distinct absorption and emission signals that did not match existing theories.

“This was a long-standing puzzle in the field,” said Colette Sullivan, a doctoral student in Rice’s Department of Chemistry and co-author of the study. “Once we connected the experimental results with theory, it became clear the two signals were coming from completely different processes.”