First Measurement of Electron Energy Distributions, Could Enable Sustainable Energy Technologies

To answer a question crucial to technologies such as energy conversion, a team of researchers at the University of Michigan, Purdue University and the University of Liverpool in the U.K. have figured out a way to measure how many “hot charge carriers”—for example, electrons with extra energy—are present in a metal nanostructure.

“For example, if you wanted to employ light to split water into hydrogen and oxygen, you can use hot charge carriers because electrons that are more energetic can more readily participate in the reaction and drive the reaction faster. That’s one possible use for hot carriers in energy conversion or storage applications,” said Edgar Meyhofer, a professor of mechanical engineering at U-M, who co-led the research.

Vladimir Shalaev, a professor of electrical and computer engineering, led the contribution from Purdue. The findings also confirm that thinner metals are more efficient at using light for generating hot charge carriers. Light can drive the motion of electrons on the surfaces of materials such as gold and silver, creating waves known as surface plasmons. These waves, in turn, can generate hot charge carriers.

The researchers compared the usual distribution of charge carrier energies to air at room temperature: The molecules in air do not all have the same energy—their average energy is reflected by the temperature. The energies of negatively-charged electrons and positively-charged holes ordinarily follow similar distributions within a material. But in materials that support surface plasmons, light can be used to give extra energy to some charge carriers as though the material were much hotter—more than 2,000 degrees Fahrenheit.

Read more at University of Michigan