The Physics Behind Light Harvesting

Light from the sun powers almost all life on our planet. Organisms that do photosynthesis, like plants, algae, and some bacteria, use proteins called light harvesting complexes (LHCs) to capture energy from sunlight. With devices like solar panels, humans can do the same. Scientists are now working to figure out how to use sunlight to generate electricity, heat, and fuel more efficiently.

Professor Seogjoo Jang of Queens College and the Initiative for the Theoretical Sciences at the Graduate Center, CUNY, recently authored two papers that dig into the physics of LHCs’ ability to harness energy from photons, or particles of light.

“This work can provide lessons and ideas for developing efficient solar energy conversion devices,” Jang said.

Jang presented the culmination of the last 20 years of his research on the LHCs of purple bacteria in The Journal of Physical Chemistry Letters. The paper takes a look at how the multiple LHCs in a bacterium pass energy from light between each other. It examines the quantum mechanical effects — the bizarre physics of tiny particles — that make the transfer so efficient.

Though scientists have studied how this transfer works for decades, Jang said, many of the details at the quantum mechanical level have remained a mystery. This study presents much of this information for the first time, specifically for aggregates of LHCs in purple bacteria. The work will help scientists understand how other photosynthetic organisms collect energy, too.

In another study, which appeared on the cover of Reviews of Modern Physics, Jang comprehensively reviewed years of research in this field. With Benedetta Mennucci of the University of Pisa, Italy, Jang analyzed the contributions scientists have made over the years to understanding how LHCs work, and the challenges that remain.

“This article will serve as an essential resource for a broad range of scientists,” Jang said.