Physicists shine a light on photon absorbency – research with potentially huge PV implications


Physicists from three U.S. universities have developed a means of observing, and potentially fine-tuning, the nature of energy transfer from light photons into materials – research that could transform the efficiency of solar PV cells.

Researchers from Emory University, the Argonne National Laboratory and Ohio University were able to observe what happened when the energy from light photons was transferred to electrons in nanolayers of gold and, according to a paper published in Nature Communications, were able to effect electronic transitions at different frequencies and through a different physical process.

Manoj Manjare, of Atlanta’s Emory University, set up an experiment in which two sequential ultrafast bursts of light were shone onto nanolayers of gold positioned at different angles, reports the EurekAlert! science website.

“The first pulse was absorbed by the gold,” says paper lead author Hayk Harutyunyan, assistant professor of physics at Emory. “The second pulse of light measured the results of that absorption, showing how the electrons changed from a ground to excited state. At a certain excitation angle, we were able to induce electronic transitions that were not just a different frequency but a different physical process. We were able to track the evolution of that process over time and demonstrate why and how those transitions happen.”

With the Nature Communications paper a proof of concept, Harutyunyan and his co-researchers plan to continue to refine their methods using gold, as well as experimenting using other materials.

The experiments were set up with the help of mathematical tools and theoretical models supplied by Stephen Gray, Gary Wiederrecht and Tal Heipern, of the U.S. Department of Energy’s Argonne National Laboratory near Chicago, with Ohio University’s Alexander Govorov also working on theoretical modelling.

“We did not use brute computational power,” Harutyunyan added. “We started with experimental data and developed an analytical and theoretical model that allowed us to use pen and paper to decode the data.”