Regensburg 2019 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 57: Organic Electronics and Photovoltaics IV - Excitonic Properties and Light-Emitting Devices
CPP 57.9: Vortrag
Donnerstag, 4. April 2019, 17:15–17:30, H18
Molecular Structure and Geometry Packing Effects on Singlet Fission Mechanism — •N. Alagna1, J. Han2, N. Wollscheid1, J.L. Perez Lustres1, J. Herz1, S. Hahn3, S. Koser3, F. Paulus3, U. Bunz3, A. Dreuw2, T. Buckup1, and M. Motzkus1 — 1Physikalisch- Chemisches Institut, Ruprecht- Karls-Universität Heidelber — 2Institut für Wissenschaftliches Rechnen, Ruprecht-Karls Universität Heidelberg — 3Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg
Efficiency limit of organic photovoltaic can be overcome by singlet fission (SF), a photo induced processes where two triplet states are formed from an excited singlet state. Molecular structure and packing arrangement are critical for SF. In this work, quantum chemistry, organic synthesis and time resolved spectroscopy are applied to rationalize how SF is effected by systematic chemical modification introduced in phenazinothiadiazoles (PTD). Substitution of an aromatic ring of TIPS-Tetracene by a thiadiazole group change in a considerable way the relative energy of S1 and T1 states. In contrast with TIPS-tetracene, SF became exothermic for PTD derivatives, which show an energy difference S1-2T1 higher of 0.44 eV. This enables SF in PTD derivatives, where the fs formation of the T-T state is identified by transient absorption spectroscopy and TD-DFT calculation. Moreover, we show via CDFT-CL calculations that dimer architecture control the strength and coaction between direct and superexchange couplings, that accelerate the SF rate constant beyond 100 fs.