Credit: Andreas WindischbacherNew imaging strategy reveals exciton characteristics in natural semiconductors, using insights into their quantum homes and potential for enhancing energy conversion materials.From solar panels on our roofings to the brand-new OLED Television screens, numerous daily electronic gadgets just wouldnt work without the interaction in between light and the materials that make up semiconductors. The method natural semiconductors work is mostly figured out by their habits in the first few minutes after light excites electrons, forming “excitons” in the material.Wiebke Bennecke. Credit: Stefan MathiasPhotoemission exciton tomography supplies the answer: right away after the exciton is generated by light, it is distributed over two or more particles. Within a couple of femtoseconds, meaning in a tiny fraction of a second, the exciton shrinks back down to a single molecule.In the future, the researchers desire to tape the habits of the excitons utilizing the brand-new technique.”Reference: “Disentangling the multiorbital contributions of excitons by photoemission exciton tomography” by Wiebke Bennecke, Andreas Windischbacher, David Schmitt, Jan Philipp Bange, Ralf Hemm, Christian S. Kern, Gabriele DAvino, Xavier Blase, Daniel Steil, Sabine Steil, Martin Aeschlimann, Benjamin Stadtmüller, Marcel Reutzel, Peter Puschnig, G. S. Matthijs Jansen and Stefan Mathias, 28 February 2024, Nature Communications.DOI: 10.1038/ s41467-024-45973-xThis research benefited from the German Research Foundation (DFG) financing for the Collaborative Research Centres “Atomic scale control of energy conversion” and “Mathematics of Experiment” in Göttingen and “Spin+X” in Kaiserslautern-Landau.
Illustration showing light amazing electrons in two particles of the natural semiconductor known as buckminsterfullerene. The freshly formed exciton (revealed by the brilliant dot) is first dispersed over 2 particles before it settles on one molecule (shown on the right in the photo). Credit: Andreas WindischbacherNew imaging strategy reveals exciton characteristics in natural semiconductors, offering insights into their quantum properties and prospective for improving energy conversion materials.From photovoltaic panels on our roofs to the new OLED television screens, lots of everyday electronic devices simply wouldnt work without the interaction between light and the materials that comprise semiconductors. A brand-new classification of semiconductors is based upon organic particles, which mainly include carbon, such as buckminsterfullerene. The way organic semiconductors work is mainly determined by their behavior in the first few moments after light excites electrons, forming “excitons” in the material.Wiebke Bennecke. Credit: Fotostudio Roman Brodel/BraunschweigResearchers from the Universities of Göttingen, Graz, Kaiserslautern-Landau and Grenoble-Alpes have now, for the very first time, made very fast and very precise pictures of these excitons– in fact, precise to one quadrillionth of a second (0.000,000,000,000,001 s) and one billionth of a meter (0.000,000,001 m). This understanding is vital for developing more effective materials with organic semiconductors.The outcomes were published recently in the scientific journal Nature Communications.Understanding Exciton DynamicsWhen light hits a product, some electrons absorb the energy and this puts them into an ecstatic state. In natural semiconductors, such as those utilized in OLEDs, the interaction in between such thrilled electrons and left-over “holes” is extremely strong, and electrons and holes can no longer be referred to as individual particles. Rather, adversely charged electrons and positively charged holes combine to form sets, called excitons.Understanding the quantum mechanical residential or commercial properties of these excitons in organic semiconductors has long been thought about a major difficulty– both from a theoretical and a speculative point of view.Dr. Matthijs Jansen. Credit: Christina MöllerThe new approach sheds light on this puzzle. Wiebke Bennecke, physicist at the University of Göttingen and first author of the study, describes: “Using our photoemission electron microscopic lense, we can recognize that the appealing forces within the excitons significantly alter their energy and speed distribution. We measure the modifications with exceptionally high resolution in both time and space, and compare them with the theoretical predictions of quantum mechanics.”The researchers refer to this new strategy as photoemission exciton tomography. The theory behind it was established by a group led by Professor Peter Puschnig at the University of Graz.Advancements in Semiconductor ResearchThis new method makes it possible for researchers, for the very first time, to both procedure and envision the quantum mechanical wave function of the excitons. Put simply, the wave function explains the state of an exciton and determines its probability of being present.Dr. Matthijs Jansen, Göttingen University, explains the significance of the findings: “The natural semiconductor that we studied was buckminsterfullerene which consists of a spherical arrangement of 60 carbon atoms. The question was whether an exciton would constantly be found on a single molecule or whether it could be dispersed across several molecules at the same time. This residential or commercial property can have a major impact on the effectiveness of semiconductors in solar batteries.”Professor Stefan Mathias. Credit: Stefan MathiasPhotoemission exciton tomography provides the answer: instantly after the exciton is produced by light, it is dispersed over 2 or more molecules. Nevertheless, within a few femtoseconds, meaning in a small portion of a 2nd, the exciton diminishes back down to a single molecule.In the future, the scientists wish to tape-record the habits of the excitons utilizing the brand-new method. According to Professor Stefan Mathias, Göttingen University, this holds potential: “For example, we desire to see how the relative motion of molecules affects the characteristics of excitons in a product. These examinations will assist us understand energy conversion procedures in natural semiconductors. And we hope that this understanding will add to the development of more effective materials for solar cells.”Reference: “Disentangling the multiorbital contributions of excitons by photoemission exciton tomography” by Wiebke Bennecke, Andreas Windischbacher, David Schmitt, Jan Philipp Bange, Ralf Hemm, Christian S. Kern, Gabriele DAvino, Xavier Blase, Daniel Steil, Sabine Steil, Martin Aeschlimann, Benjamin Stadtmüller, Marcel Reutzel, Peter Puschnig, G. S. Matthijs Jansen and Stefan Mathias, 28 February 2024, Nature Communications.DOI: 10.1038/ s41467-024-45973-xThis research benefited from the German Research Foundation (DFG) funding for the Collaborative Research Centres “Atomic scale control of energy conversion” and “Mathematics of Experiment” in Göttingen and “Spin+X” in Kaiserslautern-Landau. The group in Graz was supported by moneying from the ERC Synergy Grant “Orbital Cinema” of the European Union.
