Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 8: Electron and spin dynamics
O 8.5: Vortrag
Montag, 26. März 2012, 11:30–11:45, A 060
Singlet fission and efficient electron transfer from the ”dark” multi-exciton state in pentacene — Wai-Lun Chan1, •Manuel Ligges1,2, Askat Jailaubekov1, Loren Kaake1, Luis Miaja-Avila1, and Xiaoyang Zhu1 — 1Department of Chemistry & Biochemistry, University of Texas, Austin, TX 78712, USA — 2Fakultät für Physik, Universität Duisburg-Essen, 78756 Duisburg
Singlet fission refers to the creation of two or more electron-hole pairs from the absorption of a single photon in organic chromophores. This process holds great promise in the field of photovoltaics, because it may lead to power conversion efficiencies exceeding the theoretical limit for single junction solar cells, the so called Shockely-Queisser limit [1]. One of the key challenges in the implementation of singlet fission is the efficient extraction of charge carriers. Using time-resolved two-photon photoemission on the model system pentacene/C60, we show that the process of singlet fission is accompanied by efficient electron transfer from a multi-electron intermediate state, previously been referred to as the ” dark ” multi-exciton state [2]. In addition, we show that - contrary to common belief - singlet fission in pentacene cannot be described in terms of simple rate models but involves coherent coupling between the initially excited singlet exciton and the intermediate multi-exciton state.
[1] W. Shockley & H. J. Queisser, J. Appl. Phys. 32, 510 (1961)
[2] P. M. Zimmerman et al., Nature Chem. 2, 648 (2010)