Measured Davydov splitting in oligothiophene crystals
CNR-INFM and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 53, I-20125 Milan, Italy. The Journal of Chemical Physics
(Impact Factor: 2.95).
06/2006; 124(19):194710. DOI: 10.1063/1.2196037
The polarized absorption spectra of single crystals of oligothiophenes in a wide spectral range are reported. The experimental procedure is discussed, underlying several details which are relevant to obtain reliable spectra particularly for samples of increasing thickness. On the basis of these considerations, it has been possible to fully detect the transition to the upper Davydov exciton originating from the first molecular state. The position and shape of the main exciton peak in these materials are compared and discussed, taking into consideration the molecular arrangement and the longitudinal contribution which depends on the transition moment orientation. The Davydov splitting values as deduced from the experimental data at room temperature are also reported either for the first vibronic replica or for the electronic transition as a whole. The difference between the purely transverse and the measured Davydov splitting is discussed.
Available from: Leonardo Silvestri
- "r electronic transition . The ac polarized replicas in the spectral region between 2 . 7 and 3 . 6 eV are built on the lower b polarized excitonic band and obtain their oscillator strength through an intermolecular Herzberg – Teller coupling to the nearly free ac polarized exciton ( Silvestri et al . 2009 ; Spano 2003 , 2004 ; Spano et al . 2007 ; Tavazzi et al . 2006a ) . On the contrary , the b polarized exciton is very weakly allowed and it is more strongly coupled to phonons , showing a vibronic progression . On the basis of the calculations and the measurements in solution , other excitonic transitions are expected originating from the higher molecular electronic transitions ( Tavazzi et al . 201"
Crystallization and Materials Science of Modern Artificial and Natural Crystals, 01/2012; , ISBN: 978-953-307-608-9
Available from: S. Binetti
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ABSTRACT: Rubrene, perylene, -quaterthiophene, and tetracene single crystals were grown and placed between indium-tin-oxide and Al electrodes; the current-voltage characteristics of the so-fabricated two-terminal organic devices were measured at ambient conditions under solar simulator illumination. While rubrene single crystals do not exhibit any pho-tovoltaic effect, open-circuit voltages reach values up to 1.8 V in devices based on perylene, -quaterthiophene, and tetra-cene single crystals.
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ABSTRACT: The impact of exciton−phonon (EP) coupling including two or more vibrational modes on emission in herringbone aggregates with N molecules is investigated theoretically. When the total nuclear relaxation due to all modes is much smaller than the exciton band curvature at the band minimum, the effects of several modes are additive, with each mode contributing a single sideband to the emission spectrum in the limit of large N. Outside the weak coupling regime synergistic intermode effects arise. In particular, the presence of a strongly coupled mode enhances the sideband intensity of a weakly coupled mode. Applications are made to photoluminescence spectra of oligothiophene thin films.
The Journal of Physical Chemistry C 04/2007; 111(16). DOI:10.1021/jp067927r · 4.77 Impact Factor
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