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M. Hoffmann, K. Schmidt, T. Fritz, T. Hasche, V. M. Agranovich, K. Leo, The lowest energy Frenkel and charge-transfer excitons in quasi-one-dimensional structures: application to MePTCDI and PTCDA crystals, Chem. Phys. 258 (2000) 73-96. | |
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| Abstract | |
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We consider the exciton states in quasi-one-dimensional organic
crystals with strong orbital overlap between neighboring molecules. In
such crystals, the energy difference between the lowest Frenkel exciton
and the nearest-neighbor charge-transfer excitons becomes small and
their strong mixing determines the nature of the lowest energy states.
We discuss these effects for crystalline MePTCDI
(N-N'-dimethylperylene-3,4,9,10-dicarboximide) and PTCDA
(3,4,9,10-perylenetetracarboxylic dianhydride). To model the exciton
states we use a Hamiltonian which includes the mixing of Frenkel
excitons with several vibronic levels and charge-transfer excitons.
With appropriate fitting parameters, we demonstrate that this model can
explain the main features of the low temperature absorption spectra.
Polarized absorption spectra of MePTCDI show different polarization
ratios for the various absorption peaks. This polarization behavior is
discussed as a qualitative proof for the varying contribution of the
charge-transfer excitons, which have a transition dipole direction
different from that of the Frenkel excitons.
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| DOI:10.1016/S0301-0104(00)00157-9 (direct link to publisher) | |
| pdf file of manuscript version | |
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homepage M. Hoffmann | |
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| last updated: M. Hoffmann, Dec 2007 |