Phys.org April 14, 2023
In a usual solar cell, the energy of a single photon is transferred to two free charges in the material. However, a few molecular materials like pentacene are an exception and show conversion of one photon into four charges, instead. This excitation doubling, which is called exciton fission, could be extremely useful for high-efficiency photovoltaics, specifically to upgrade the dominant silicon-based technologies. An international team of researchers (Germany, Canada) used time- and angle-resolved photoemission spectroscopy to observe the primary step of singlet fission in crystalline pentacene. Their results indicated a charge-transfer mediated mechanism with a hybridization of Frenkel and charge-transfer states in the lowest bright singlet exciton. Gaining knowledge about the localization and the orbital character of the exciton wave functions recorded in momentum maps allowed them to directly compare the localization of singlet and bitriplet excitons and decompose energetically overlapping states based on their orbital character. According to the researchers orbital- and localization-resolved many-body dynamics promise deep insights into the mechanics governing molecular systems and topological materials… read. Open Access TECHNICAL ARTICLEÂ
Orbital-projected dynamics and evolution at longer delays. Credit: Nature 616, 275–279 (2023)