Exciton fission – one photon in, two electrons out
by Staff Writers
Berlin, Germany (SPX) May 07, 2023
Unraveling the Mystery of Exciton Fission
“When pentacene is excited by light, the electrons in the material rapidly react,” explains Prof. Ralph Ernstorfer, a senior author of the study. “It was an open and very disputed question whether a photon excites two electrons directly or initially one electron, which subsequently shares its energy with another electron.”
Employing Cutting-Edge Techniques for Observation
To unravel this mystery, the researchers employed time- and angle-resolved photoemission spectroscopy, a cutting-edge technique to observe the dynamics of electrons on the femtosecond time scale, which is a billionth of a millionth of a second. Consequently, this ultrafast electron movie camera enabled them to capture images of the fleeting excited electrons for the first time, thereby providing crucial insights into exciton fission dynamics.
The Significance of Visualizing Electrons
“Seeing these electrons was crucial to decipher the process,” says Alexander Neef, from the Fritz Haber Institute and the first author of the study. “An excited electron not only has a specific energy but also moves in distinct patterns, which are called orbitals. Thus, it is much easier to tell the electron apart if we can see their orbital shapes and how these change over time.”
Insights Gained from Ultrafast Electron Movies
With the images from the ultrafast electron movie at hand, the researchers decomposed the dynamics of the excited electrons for the first time based on their orbital characteristics. Consequently, “We can now say with certainty that only one electron is excited directly and identified the mechanism of the excitation-doubling process,” adds Alexander Neef. This detailed understanding marks a significant advancement in the study of exciton fission dynamics.
Implications for Photovoltaic Applications
Knowing the mechanism of exciton fission is essential to using it for photovoltaic applications. For instance, a silicon solar cell enhanced with an excitation-doubling material could boost the solar-to-electricity efficiency by one-third. Consequently, such an advance could have enormous impacts since solar energy will be the dominant power source of the future. Therefore, large investments are already flowing into the construction of these third-generation solar cells.
https://www.spacedaily.com/reports/Exciton_fission___one_photon_in_two_electrons_out_999.html
