New technology follows dark excitons for future solar cells
How can modern technologies, such as solar cells, be optimized? An international team of researchers, led by the University of Gotingen, starts this question with the help of an innovative new technology. For the first time, the formation of small, elusive particles – known as dark excitons – is accurately followed in both time and space. These invisible energy carriers are ready to play a crucial role in the development of future solar cells, LEDs and detectors. The findings were published in Nature Photonics.
Dark excitons are extremely small pairs consisting of an electron and the hole that it leaves when it is excited. Despite wearing energy, these particles do not emit light, so they are called ‘dark’. A way to think of an exciton is like a balloon (the electron) flying away, leaving an empty space (the hole) behind, both still connected by a Coulomb interaction power. Although difficult to detect, dark excitons are especially important in atomically thin, two -dimensional structures that are found in certain semiconductor materials.
Earlier, Professor Stefan Mathias and his research group of the Faculty of Physics at the University of Gotteningen showed how dark excitons are made in an incredibly short period of time, which describe their dynamics using the quantum mechanical theory. Now, in their latest study, the team has introduced a groundbreaking method called “Ultrasle Dark-Field Momentum Microscopy.” For the first time, this technique has enabled them to observe the formation of dark excitons in materials such as tungsten dismissal (WSE2) and Molybdendendisulfide (MOS2). Amazingly enough, the formation process takes place in just 55 femtoseconds (0.0000000000055 seconds), measured with a resolution of 480 nanometers (0.00000048 meters).
“This method enabled us to precisely measure the dynamics of load carriers,” said Dr. David Schmitt, first author and physicist at the University of Getsingen. “The results offer a fundamental understanding of how the properties of materials influence the behavior of these load carriers. In the future, this technique can be used to improve the efficiency and quality of solar cells, for example.”
Dr. Marcel Reutzel, leader of Junior research group at Gotingen, added: “This technique can not only be applied to specially designed systems, but also to exploring new types of materials.”
Research report:Ultrasnelle Nano image of dark excitons
