In a study published in Sciences Advances just recently, researchers from the FHI, the MPSD and the Julius-Maximilians-Universität Würzburg have handled to track how particles in a crystalline material construct from pentacene particles move throughout the SEF process, utilizing a speculative strategy called “femtosecond electron diffraction.” Such a method can record snapshots of the atomic structure in real-time as the SEF process unfolds. In order to be able to capture these photos in pentacene, a product which only contains small and light atoms, the measurements had to reach an extraordinary stability and resolution..
” We have brought such experiments to a point where they can treat these products, which is very exciting for chemistry, biology, and products science. These measurements have actually revealed that genuinely collective molecular motions accompany the SEF procedure in pentacene. Particularly, an ultrafast delocalized oscillation of pentacene molecules has been identified, which assists in efficient energy and charge transfer throughout big ranges,” says Heinrich Schwoerer from the MPSD.
Thanks to modern theory, the team had the ability to reveal the molecular motions included in the preliminary excitation event and how these motions set off more complicated molecular motions involving lots of molecules of the crystal. “Our theory analysis could fix very intricate molecular movements. We might determine a dominant one that includes particles sliding with regard to each other, which can only be activated through the coupling of electronic excitations to other more localized molecular movements, that then, in turn, couple to this essential motion also observed in experiment,” says Mariana Rossi from MPSD..
These cumulative atomic movements observed by the group involved in the task may well be the secret to describe how the two excitons generated from the SEF process can separate, which is a requirement to collect their charges in a solar power device. “Simply put, our picture is that these molecular movements effectively neutralize the forces that keep the two excitons together right after they have actually been generated, offering a possible explanation about the origin of the ultrafast timescales associated with the fission, and consequently facilitate the high effectiveness of solar to electrical energy conversion,” states Hélène Seiler, a postdoctoral fellow at the FHI in the group of Ralph Ernstorfer.
According to Sebastian Hammer of the chair Experimental Physics VI at the University of Würzburg, the groups work will have a larger effect: ” Beyond supplying essential insights into the SEF process, this work reveals that it is possible to expose the atomic movement in more intricate, functional organic products, which are fragile and composed of light atoms.”.
Referral: “Nuclear dynamics of singlet exciton fission in pentacene single crystals” by Hélène Seiler, Marcin Krynski, Daniela Zahn, Sebastian Hammer, Yoav William Windsor, Thomas Vasileiadis, Jens Pflaum, Ralph Ernstorfer, Mariana Rossi and Heinrich Schwoerer, 25 June 2021, Science Advances.DOI: 10.1126/ sciadv.abg0869.
In the singlet exciton fission procedure, a singlet exciton (blue) is produced upon soaking up light and then divides into two triplets (red) on ultrafast timescales. The group tracked the real-time molecular movements acompanying this process in single crystals of pentacene. Certain natural molecular solids have the strange capability to substantially increase the solar to electrical power conversion efficiency, thanks to a process called singlet exciton fission (SEF). These measurements have actually exposed that really cumulative molecular movements accompany the SEF procedure in pentacene.
In the singlet exciton fission procedure, a singlet exciton (blue) is developed upon soaking up light and after that splits into 2 triplets (red) on ultrafast timescales. The group tracked the real-time molecular movements acompanying this process in single crystals of pentacene. Credit: © Jörg Harms, MPSD
Researchers from the Fritz Haber Institute (FHI) in Berlin, the MPSD and the Julius-Maximilians-Universität Würzburg have actually provided crucial new insights into an essential procedure for the development of more efficient solar cells and other light-based innovations, called singlet exciton fission. They have managed to track how molecules of a promising material, single crystals consisted of pentacene particles, relocation in real time as singlet fission happens, showing that a cumulative motion of molecules may be the origin of the fast timescales connected to this process.
Certain organic molecular solids have the strange ability to substantially increase the solar to electrical power conversion efficiency, thanks to a procedure called singlet exciton fission (SEF). In this process two electron hole pairs, which are called excitons, are generated by the absorption of one light quantum (a photon).
The efficiency and speed of the SEF process are determined by subtle details related to the method molecules arrange themselves in the product. Despite hundreds of studies on the topic, however, there had actually been no other way to observe in real time how precisely the molecules move in order to help with the SEF occasion. Understanding this little the puzzle is vital to optimize SEF products and further increase their performance..